The Fourth Round Rumble (Japanese: くさのフィールド！いがいなきょうてき！Grass Field! Unexpected Rival!) is the 77th episode of the Pokémon anime. It was first broadcast in Japan on January 1, 1999 and in the United States on November 13, 1999.
Ash's fourth battle on the Grass Field is against his toughest opponent yet! He battles Jeanette Fisher from Crimson City who brings a whole cheering section with her. Jeanette uses a powerful Scyther, which Ash has never battled before. Will his Bulbasaur be able whip Scyther's double team attack by using his reliable vine whip? To finish off the match, Jeanette brings out her Bellsprout which Ash feel is far inferior to his Pokémon. Once again, Ash lets his over-confidence take over.
Ash, Pikachu, Misty, and Brock watch Gary's fourth round match on the Rock Field, and are shocked when Gary is abruptly defeated by a Trainer named Melissa. This leaves Ash worried about his own chances during the fourth round, though Brock and Misty cheer him on. He later learns from Professor Oak that all of Pallet Town is cheering him on, which only makes him more nervous. Meanwhile, Team Rocket opens up a souvenir stand with the intent of luring in and stealing Pokémon from Trainers.
At the Grass Field, Ash starts his next match with Jeanette Fisher from Crimson City. He sends out Bulbasaur, and Jeanette uses Beedrill. The Bug-type Pokémon is about to hit Bulbasaur with Poison Sting, but Bulbasaur dodges it. Bulbasaur uses Razor Leaf, but Beedrill counters with Twineedle. Bulbasaur dodges the attack again. Ash then has Bulbasaur use Leech Seed, which instantly drains Beedrill's energy, before having Bulbasaur finish it off with Tackle. Jeanette then sends out her next Pokémon, Scyther. Bulbasaur launches a Razor Leaf at it, but Scyther uses Double Team to evade. Scyther gets in a few hits before Ash gets the idea to use Vine Whip on all the duplicates, so Bulbasaur will eventually hit the real one. The plan works, and Scyther is knocked out.
Unwavering, Jeanette calls on her last Pokémon, a Bellsprout. Ash laughs and calls it weak as the Flower Pokémon wiggles its body in an odd manner. Bulbasaur uses Tackle, but Bellsprout evades the attack with ease. It then picks up Bulbasaur, repeatedly slams him into the ground, and knocks Bulbasaur out, shocking Ash. Brock realizes that Jeanette's Bellsprout must be exceptionally trained, or else it would not be used in a League battle. Ash sends out Pikachu, and he uses Thunder Shock, but Bellsprout dodges the attack and uses Razor Leaf. Pikachu dodges it and tries to use Thunderbolt, but Bellsprout's roots keep him ingrained and immune to Electric attacks. Pikachu tries to punch and box-kick Bellsprout, but it slams him again and defeats him.
Down to his last Pokémon, Ash pauses for a second and then sends out his Muk, surprising his friends. Muk is able to absorb Bellsprout's Slam and Razor Leaf attacks with ease, then uses a Body Slam. Its powerful stench and weight smothers Bellsprout, and it soon faints. Ash wins the battle, and has now cleared all four preliminary fields to advance through to the next round of competition.
Gary is revealed to have made it to the fourth round.
Gary loses his fourth round battle against Melissa, placing him in the Top 32.
For a split-second during the cut between the commercial break and the first half of the "Who's That Pokémon" segment, the first quarter second of the Japanese "Who's That Pokémon" segment can be seen. Though mostly obscured by the dubs whiteout transition effect, one can clearly make out the Japanese "Pocket Monster" logo in the lower right-hand corner.
When Gary loses and bids farewell to Ash in the original, he talks about not being smiled upon by the goddess of fortune and that his girls' tears are the only award he needs. In the dub, he talks about being distracted by their cheering but reassures them they will get over it.
Ash asks Pikachu if they should drop out in the dub, but in the original version, he simply wonders if he can win.
When Officer Jenny commands her Growlithe to use Flamethrower, she incorrectly refers to it as Arcanine in the dub, and its cry is also identical to the Arcanine in the previous episode. However, this error is corrected in Castilian Spanish dub.
In the dub, Misty says that she doesn't know whether it was more surprising for her that Ash chose to use Muk or the fact that he thought ahead, while in the Japanese version, she says that she had thought that Ash was an idiot and commends him on having a strategy.
Team Rocket concludes the episode with a fast food-themed version of their motto in the dub. In the original, the motto is unchanged until the last two lines.