"So Long Sucker" is the twentieth episode of the Adventures of Sonic the Hedgehog television series. Despite being produced as the twentieth episode, it originally aired as the eighteenth episode during the show's original run.
Sonic is out running when he sees an a strike of lightning opens up an interdimensional portal. A small black glob type creature comes through the portal and follows Sonic to a place where Tails is preparing Chili Dogs for lunch. Tails likes the creature and decided to name him Goobster and keeps him as a pet. Goobster eats all their Chili Dogs.
Scratch and Grounder attack in fighter planes and Goobster helps Sonic to defeat them. Goobster gets hungry so Sonic offers him steak and a sandwich, but Goobster only wants Chili Dogs. Goobster becomes large and starts sucking up everything in sight. Sonic gives him his retirement chili dogs and Goobster calms down.
Dr. Robotnik is angry that Scratch and Grounder failed once again. Scratch and Grounder say it was because of Goobster. Robotnik tells them to kidnap Goobster to lure Sonic and Tails into a trap.
Sonic figures out that Goobster is from another dimension, but before he can do anything about it, Goobster is captured by Scratch and Grounder.
In Dr. Robotnik's Lair, Goobster starts to eat everything in sight. Robotnik decides to use Goobster to get rid of Sonic and take over Mobius. When Sonic and Tails arrive, Goobster is hooked up to an electric machine that shocks him and makes him start sucking up everything. He quickly sucks up Sonic and Tails, but then burps them back out. Sonic frees Goobster and the three escape.
It begins to rain and Sonic takes them back to where he first saw the interdimensional portal open. They wait for lightning to strike again, but Robotnik and his badniks attack. Sonic uses Grounder as a conductor and lightning strikes, opening the portal. Goobster goes through the portal where he is happily reunited with his parents. Tails is sad to see him leave, but Sonic cheers him up by saying he can get a new pet.
Sonic teaches Tails about the responsibility of owning a pet.