In the main series
Major appearances
Voltorb debuted in The Ninja Poké-Showdown. Koga kept a bunch of them in his Gym as booby traps. They were later targeted in one of Team Rocket's schemes.
Multiple Voltorb appeared in So Near, Yet So Farfetch'd. Team Rocket received them from Keith, thinking they were Poké Balls with rare Pokémon hidden inside them, as well as their Arbok, Lickitung, and Weezing. When Team Rocket found out they were not, the Voltorb started to explode in their balloon. They dumped most of the Voltorb on the thief, prompting him to quit his crime spree, but a single Voltorb sent them blasting off.
A Voltorb lived amongst Electrode in The Underground Round Up. Although Misty was terrified of it, the Electric-type befriended her Togepi, and the baby Pokémon was sad when it had to leave.
Three Voltorb appeared in Love, Pokémon Style, where they were rolling down a hill before they were caught by Ash's Kingler. However, they shocked and injured it in the process.
Wattson used a Voltorb in his Gym battle with Ash in Watt's with Wattson?. It was easily defeated by Pikachu, who had become super-charged during an incident at the Mauville Gym. Multiple wild Voltorb also appeared later on in the episode.
Multiple Voltorb appeared in Bucking the Treasure Trend, where they attacked Ash, his friends, and Buck as they searched for Dandelion Island's treasure.
A Voltorb appeared in the Hoopa's Surprise Ring Adventures short Ball Pickup. It was thrown at Ash as part of a prank by Hoopa, but it then attacks the both of them, as well as Pikachu and Hawlucha, with Self-Destruct.
Minor appearances
A Voltorb appeared in Duplica's flashback in Ditto's Mysterious Mansion, where it came onstage as her Ditto tried to transform into one.
A painted Voltorb appeared in Pokémon Fashion Flash as one of the Pokémon seen on Scissor Street.
A Voltorb appeared in A Chansey Operation, where it was stuck in a Weepinbell's mouth that Misty and Jessie had to pull out from.
A Voltorb appeared as an image in the dubbed version of The Ultimate Test.
A Voltorb appeared in The Breeding Center Secret.
Multiple Voltorb appeared in Showdown at the Po-ké Corral, where they were among the Pokémon living at Professor Oak's Laboratory.
A Voltorb appeared in Pikachu's Vacation as one of the Pokémon seen at the Pokémon Theme Park.
A Voltorb appeared in Pallet Party Panic as one of the Pokémon at a party in Pallet Town.
A Trainer's Voltorb appeared in The Lost Lapras, where it was among the Pokémon brought to the Pokémon Center.
A Voltorb appeared in Pikachu Re-Volts, where it was among the Pokémon controlled by Cassidy and Butch at Mandarin Island North.
A Voltorb appeared in The Power of One.
A wild Voltorb appeared in Pikachu's Rescue Adventure.
A Voltorb appeared in Tricks of the Trade as one of the Pokémon seen at the Pokémon Swap Meet in Palmpona.
A Trainer's Voltorb appeared in Wired for Battle! as an image that came up in Shingo's laptop.
A Voltorb appeared in Pikachu & Pichu as a resident of Big Town.
A Voltorb appeared in The Fortune Hunters as one of the Pokémon stolen by Butch and Cassidy.
Multiple Voltorb appeared in The Legend of Thunder!, where they were among the Electric-type Pokémon lured by the "Miracle Crystal" that Attila and Hun were using.
A Voltorb appeared in As Clear As Crystal as one of the Pokémon affected by a crystal that gave a lake the ability to heal Electric-type Pokémon.
A Voltorb appeared in the opening intro of Celebi: The Voice of the Forest, which was reused for Pokémon Heroes: Latios & Latias.
Two Voltorb appeared in You're a Star, Larvitar!, both under the ownership of a Trainer.
A Voltorb appeared in Gonna Rule The School!, under the ownership of the Pokémon Trainers' School. It was temporarily loaned to one of the school's underage students for use.
A Voltorb made a cameo appearance in Pearls are a Spoink's Best Friend. Spoink mistook it for a pearl.
Multiple Voltorb appeared in Destiny Deoxys.
A Coordinator's Voltorb appeared in Deceit and Assist.
In May's Egg-Cellent Adventure, two Voltorb attacked May as they are trained to do so when anyone steps foot on Nicolette's property.
A Voltorb disguised as a watermelon appeared in the ending credits of Arceus and the Jewel of Life. It exploded when Jessie and James picked it up after falling for its disguise.
A Voltorb appeared in A Campus Reunion!.
Seven Voltorb appeared in The Future Is Now, Thanks to Determination!, where they were among the Electric-type Pokémon being controlled by Team Rocket.
A Voltorb appeared in Volcanion and the Mechanical Marvel.
A Voltorb appeared in I Choose You!.
A Voltorb appeared in Currying Favor and Flavor! in a dream that Ash was having.
Pokédex entries
In Pokémon Origins
A Voltorb appeared in File 3: Giovanni, under the ownership of a Trainer who Red defeated in a battle.
In the Pokémon Adventures manga
Voltorb debuted in Danger: High Voltorb, where Red tried to touch one aboard the S.S. Anne, thinking that it was only a Poké Ball, but wound up being zapped by it.
Multiple Voltorb appeared in Go for the Golbat, under the ownership of Lt. Surge. They were used in conjunction with multiple Electrode to shock Red and as projectiles.
In The Coming of Slowpoke (Eventually), Ken of the Team Rocket Elite Trio used a Voltorb along with its evolved form, Electrode, to battle against Yellow.
Wattson's Voltorb was only seen in Plugging Past Electrike I, inside the Power Plant located in New Mauville.
A Voltorb appeared in Encountering Elekid.
A Voltorb appeared in Clobbering Claydol, under the ownership of a Guitarist.
Jet owns a Voltorb that he uses in the Pokéathlon Speed Course in Out-Odding Oddish.
Multiple Voltorb were among the Electric-type Pokémon that charged the Prism Tower during a blackout in Pangoro Poses a Problem.
In the Pokémon Gold & Silver: The Golden Boys manga
A Voltorb appeared in the intro of Let's Go! The Journey Towards The Championship.
Multiple Voltorb appeared in Let's Aim For The Goal!, under the ownership of Firebreather Takeo.
In the Pokémon Pocket Monsters manga
Lt. Surge's Voltorb battled Clefairy and evolved in the same match in Great Success in the Mountains or the Seas!?.
Green caught a Voltorb before participating in the sports meet in Pokémon Sports Meet!!.
Blaine has many Voltorb that were used in the first part of the Pokémon Quiz Battle in Fierce Competition at the Pokémon Quiz Battle!!.
Giovanni sends out Voltorb to prevent Red from interfering with his plans on creating Mewtwo in Bring Down the Strongest Pokémon!!.
A Voltorb is seen with Red during the curry cooking competition that went on in Curry Showdown! Which is the Most Delicious?.
A Voltorb appeared in PMDP16.
A Trainer's Voltorb appeared in PMHGSS11.
A Voltorb appeared in PMHGSS18.