Bulbasaur first appearance was in Bulbasaur and the Hidden Village. When Misty tried to capture a wild Oddish, Bulbasaur rushed to Oddish's aid, easily defeating both her Starmie with Tackle and Ash's Butterfree by blowing his own Sleep Powder back onto him.
Later, the group met Melanie, who cared for sick, injured, and abandoned Pokémon in the Hidden Village. She revealed that she had raised Bulbasaur, that it acted as the village's bodyguard, and was blatantly hostile to all Trainers.
Later, Team Rocket attacked the village and attempted to steal all of the Pokémon with an enormous vacuum. Bulbasaur managed to save Oddish at the last second, and was touched when Ash dashed out to help him get to safety. It then used Vine Whip to deflect the vacuum and Pidgeotto drove Team Rocket away. After Team Rocket's defeat, Melanie encouraged Bulbasaur to join Ash, explaining that its growth was being stunted by staying too long in the village. Bulbasaur agreed to join him once Ash defeated it in battle. Bulbasaur put up an excellent fight against Pikachu, using its vines to seize and smash Pikachu onto the ground repeatedly. However, a powerful Thunderbolt fried Bulbasaur and stunned it long enough for Ash to capture it.
Bulbasaur was first used in a battle to repel Team Rocket Grunts aboard the St. Anne in Battle Aboard the St. Anne, where it joined a group of other Bulbasaur to use Vine Whip on the Grunts. Its vines were also used to help the gang and Team Rocket escape from the sinking ship in the next episode.
Bulbasaur's Gym battle debut occurred in Pokémon Scent-sation!, where it fought Erika's Tangela. It attempted to use Vine Whip, but Tangela used Constrict to pull it in close and defeated it with Stun Spore.
In The Ninja Poké-Showdown, Bulbasaur was used to battle Koga's sister, Aya, and her Venonat. After dodging Bulbasaur's Tackle, Venonat fired its Stun Spore. Bulbasaur, however, countered by blowing away the spores and used Vine Whip. Venonat was able to dodge Bulbasaur's vines and hit bulbasaur with a super-effective Psybeam. Bulbasaur, however, was able to endure the hit and after dodging another Psybeam it defeated Venonat with Leech Seed.
In Ditto's Mysterious Mansion, Bulbasaur was called out by Ash to battle Duplica's Ditto. Ditto immediately transformed into Bulbasaur and blocked an incoming Razor Leaf with Vine Whip. It then used Vine Whip to enwrap Bulbasaur. Unable to do anything, Ash forfeited the match.
In Who Gets To Keep Togepi?, Ash used Bulbasaur in the tournament to decide who got to keep Togepi. It faced Misty's unintentional entrant Psyduck and easily defeated the Duck Pokémon by licking and tickling it. However, the win meant nothing as Togepi chose Misty as its Trainer anyway.
Ash's Bulbasaur resisting evolution
Bulbasaur had the opportunity to evolve in Bulbasaur's Mysterious Garden. Bulbasaur was used in a battle against a Hiker's Rhyhorn. While Rhyhorn headed forwards using Take Down, Bulbasaur tried stopping it with Leech Seed. Bulbasaur, however, failed to do so and was hit hard. Ash tried recalling Bulbasaur, but it refused to return to its Poké Ball, wanting to continue the battle. As Rhyhorn charged in for another attack, Bulbasaur struck it with Razor Leaf and followed up with Vine Whip, knocking it out. Ash then noticed Bulbasaur had collapsed and that its bulb had started glowing and immediately rushed to the Pokémon Center. At the Pokémon Center, Nurse Joy revealed Bulbasaur was almost ready to evolve and that the evolution of Bulbasaur takes place at a special festival in the Mysterious Garden. That night, Pikachu noticed Bulbasaur leaving the Pokémon Center and the two had a conversation. Suddenly, Bulbasaur was grabbed by multiple vines belonging to a group of Bulbasaur and was taken away. While Pikachu went to get the others, Bulbasaur was taken to the Mysterious Garden where the evolutionary festival was about to take place. While all other Bulbasaur evolved into Ivysaur, Ash's Bulbasaur refused to do so, despite facing the mass of Ivysaur as well as a Venusaur, who were angry at it for ruining the festival. Ash then intervened and stood up for Bulbasaur and its decision not to evolve. Then Team Rocket appeared and used a vacuum to try to capture all Ivysaur and Venusaur. Since Bulbasaur didn't evolve, it was able to learn Solar Beam and used its new move to free the Ivysaur and blast Team Rocket off. Venusaur then approached Bulbasaur and extended a vine to it as a gesture of respect. Bulbasaur, Ash and the others then left the garden, having made amends with the Ivysaur and Venusaur.
In Princess vs Princess, Bulbasaur, along with Pikachu and Brock's Vulpix, was briefly lent to Misty to allow her to compete in the Queen of the Princess Festival contest with a more balanced team. In the first round of the tournament, Bulbasaur single-handedly defeated a Trainer's Kingler, Pinsir, Cubone and Raticate. Later, it was also seen defeating a Graveler. Bulbasaur was called out again in the finals to battle Jessie's Lickitung. Bulbasaur tried attacking with Vine Whip, but its vines were tied by Lickitung's huge tongue got and licked, causing it to faint.
In Battle for the Badge!, Bulbasaur was sent out to fight Team Rocket, who were fighting in Giovanni's stead in the Viridian Gym. It faced Giovanni's Kingler. Despite the type-advantage, Bulbasaur was hit hard by Kingler, who blocked Vine Whip with Harden and then hit back with Bubble.
Bulbasaur had only one battle in the Indigo Plateau Conference, in The Fourth Round Rumble against Jeanette Fisher. Bulbasaur first faced Jeanette's Beedrill. Beedrill started off with Tackle, but Bulbasaur managed to dodge it and retaliated with Razor Leaf. Beedrill, however, used its great speed to dodge the attack and force Bulbasaur to take evasive actions by continuously attacking with Twineedle and Poison Sting. Eventually, Bulbasaur managed to fire off a Leech Seed, crippling Beedrill giving it the chance to finish the Poison Bee Pokémon off with Tackle. Jeanette's next Pokémon was Scyther, which produced similar trouble for Ash as Bulbasaur was forced to dodge Scyther's speedy Slash and Swift attacks. Bulbasaur tried stopping Scyther with Vine Whip, but it simply knocked its vines away while continuing to attack. Scyther then went for Double Team, confusing Bulbasaur. Ash ordered Bulbasaur to attack with Vine Whip, but it only hit the clones, giving Scyther the chance to hit Bulbasaur with Slash. Scyther continued to use this strategy to constantly hit Bulbasaur, giving it no time to succesfully counterattack. As Bulbasaur was thrown in the air by another hit, Ash had Bulbasaur use Vine Whip to hit every single clone and knock out the real Scyther. Looking set to sweep the match with just Bulbasaur, Ash then took on Jeanette's Bellsprout. Bulbasaur used Tackle, but Bellsprout was able to absorb the attack using its flexible body, before seizing Bulbasaur and slamming it onto the ground until it fainted.
In Pallet Party Panic, Ash decided to take Bulbasaur, along with some of his other Pokémon, to the Orange Archipelago with him.
In Navel Maneuvers, Bulbasaur was used in the second round of Ash's Gym challenge against Danny. It attempted to help Pikachu carve a frozen geyser into an ice sled, but was unable to keep up with Danny's team until Charizard completed it in a few short Flamethrowers. Bulbasaur was later used again in the final round, where it helped Ash, Pikachu and Squirtle in the sled race down the cliff, using its vines to steer. Thanks to everyone's cooperation, Ash was able to cross the finish line first, winning Ash the challenge and earning him the Sea Ruby Badge.
In The Mystery Menace, due to one of Team Rocket's schemes, Ash and his friends found themselves in the sewers of Trovitopolis, where they came across a giant vined creature. Ash sent out Bulbasaur to attack the creature, but it used its vines to deflect Bulbasaur's Razor Leaf and then proceeded to grab and take Bulbasaur underwater. After learning more about the vined creature from the Mayor of Trovitopolis as well as about his plans to exterminate it, the group decided to head back to the sewers to save the creature and Bulbasaur from the Mayor's personal SWAT team. With help from Muk, Ash was able to find Bulbasaur and its captor, a mutated giant Bulbasaur that had been abandoned by the town's Mayor. Bulbasaur later saved its new friend by helping it sending the Mayor and the SWAT team flying.
In Misty Meets Her Match, Ash had Bulbasaur, alongside Pikachu and Squirtle, destroy a succession of targets in order to challenge Rudy to a Gym battle. The next day, Ash used Bulbasaur in the second round, the Grass-type round, of his Gym battle against Rudy, where it fought against Rudy's Exeggutor. Exeggutor was able to dodge Bulbasaur's Razor Leaf attacks using its dance moves and then knocked Bulbasaur down with Egg Bomb. While being cornered by Exeggutor, Bulbasaur quickly saved the battle by putting Exeggutor to sleep with Sleep Powder. As Exeggutor was unable to battle, the second round victory went to Ash.
In Enter the Dragonite, Ash used Bulbasaur as his fifth Pokémon in a Full Battle against Drake for the Orange League championship. It faced off against Drake's Electabuzz. Bulbasaur managed to shake off a Thunder Shock and then hit Electabuzz with Razor Leaf. Its leaves, however, were then destroyed by Thunderbolt and although Bulbasaur managed to get a hit in with Tackle, it was struck by Electabuzz's Thunder Punch, knocking it out. Drake was eventually defeated and Bulbasaur joined the rest of Ash's team in the Orange League Hall of Fame.
Bulbasaur joined Ash in Johto, where it first met Heracross in A Sappy Ending. This began the recurring joke of Heracross wanting to suck the pollen from Bulbasaur's bulb. Throughout the Johto journeys, Bulbasaur's oldest team members Charizard and Squirtle both went into training with others, leaving Bulbasaur as Ash's only remaining Kanto starter. In The Chikorita Rescue, Bulbasaur was used to battle against a Chikorita that Ash had interest in catching. It was recalled after being hurt by the small Grass-type Pokémon and was congratulated by Ash for its effort. Bulbasaur was used in Chikorita's Big Upset, where Ash ordered it to find Chikorita. It would again be irritated by Heracross, who after getting deployed by Ash against Team Rocket, wasted no time in trying to suck the pollen out of Bulbasaur's bulb. Bulbasaur scolded its teammate and hit Heracross with its vines.
It bid a solemn farewell to Squirtle in The Fire-ing Squad!. Bulbasaur fought for Ash against Misty for the second time in The Totodile Duel. It seemingly defeated Poliwag with a Razor Leaf, but Poliwag evolved into Poliwhirl and fought back with a powerful Body Slam. After taking damage from Bubble, Bulbasaur flattened Poliwhirl with Solar Beam, winning the match for Ash. It also had a rematch with Aya in Ariados, Amigos!, using Tackle to defeat Venonat from above. In The Grass Route, Bulbasaur was entered in the 45th annual Grass Tournament, reaching the finals after Team Rocket was disqualified for dressing Meowth up as a Sunflora. Bulbasaur looked set to win the final, but Ephraim's Skiploom learned Solar Beam and won the tournament.
Bulbasaur remained with Ash until Bulbasaur... the Ambassador!, when it was sent back to Professor Oak's lab to keep the Pokémon there from quarreling with each other. It proved to be a natural leader, first solving the territorial disputes between the warring Bellossom and Jumpluff factions, and the Grass-type and Water-type Pokémon by ordering and leading the construction of a new lake. It came very close to peril when it saved an Oddish from an enormous falling boulder, but revealed that it had learned Dig just in time to save itself. Oak remarked to Tracey that Bulbasaur was a perfect example of a Pokémon being able to call on powers unheard of in extreme situations. After resolving this dispute, Ash and Oak agreed to allow Bulbasaur to reside at Oak's lab for an indefinite period, finally rotating it out of his team.
It was called on in Tie One On!, where it fought in the Silver Conference against Jackson's Shiny Magneton. It quickly learned from Pikachu and Cyndaquil's mistakes, instead using a spinning Vine Whip to mow through the afterimages from Double Team. It blocked Magneton's attacks with Razor Leaf and Vine Whip, before taking it down with Leech Seed and Vine Whip. It then took on his Meganium, with whom it had a bitter rivalry after the Herb Pokémon had mocked it earlier. Neither Pokémon attempted to dodge the other's attacks, both willing to be able to take as much as the other. It came down to a battle of Vine Whips and a double Solar Beam, which knocked out both Pokémon.
Bulbasaur was seen in Showdown at the Oak Corral, and was one of the first Pokémon to realize there was something wrong. It later defeated Butch's Hitmontop and used a Solar Beam on the whole group.
In Hokey Poké Balls!, May showed her Bulbasaur to Professor Oak, which made Ash decide to bring his Bulbasaur over for a visit. When the Poké Ball arrived though, it wouldn't open, making everyone believe that the Pokémon Center's balls had been stolen. It was revealed to be Team Rocket, who accidentally dropped Ash's Bulbasaur while escaping. The two Bulbasaur teamed up to stop Team Rocket, with Ash's Bulbasaur teaching May's along the way. Once they found Team Rocket, the Bulbasaur battled against them, with Ash's Bulbasaur protecting and teaching May's how to fight. After rescuing the Pokémon, Professor Oak called back and asked for Ash's Bulbasaur to return and stop the Water and Grass Pokémon from fighting. Ash sent his Bulbasaur back to Professor Oak's Laboratory as May's Bulbasaur appeared to have made a positive change from the experience.
Kanto Battle Frontier
Bulbasaur later returned in The Right Place and the Right Mime, where May decided to leave her Bulbasaur at Professor Oak's so she could learn from Ash's Bulbasaur.
In Gathering the Gang of Four!, Ash brought it to his team alongside Charizard and Squirtle to battle Brandon at the Battle Pyramid. After Brandon's Dusclops took down Charizard, Ash's Bulbasaur was sent out to fight in the next episode. It took damage from the powerful Dusclops, including a Confuse Ray which sent the vines out of control and caused them to attack Bulbasaur and Ash. Bulbasaur responded to Ash's cries and broke out of confusion, leaping into the air and taking down Dusclops with Solar Beam. After Solrock took down Squirtle, Bulbasaur was sent back out. After taking damage from Psychic-type moves and responding with Razor Leaf and Vine Whip, a double Solar Beam knocked both Pokémon out. After Ash won, Bulbasaur returned to Professor Oak's Laboratory.
Bulbasaur made a cameo in An Old Family Blend! at Professor Oak's Laboratory, where Heracross was sucking sap from its bulb, much to Bulbasaur's annoyance. It used Vine Whip to shove Heracross away. Bulbasaur was not called upon for the Lily of the Valley Conference.
Bulbasaur appeared in a flashback in The Fires of a Red-Hot Reunion!.
Bulbasaur later appeared in The Dream Continues! at Professor Oak's corral, where it was being filmed by Alexa. It later had a happy reunion with Ash and Pikachu, before signalling to Ash's Unova Pokémon with its Solar Beam. It later posed with the rest of Ash's Pokémon in a group photo with him.