'Dr. Forrest' (name revealed in "Slide Whistle Stooges" and "Shuffleboarding") is a purple-colored fish doctor who is seen in various situations and roles throughout the series. He wears a white buttoned coat and glasses.
He first appeared in "I Was a Teenage Gary," where he told SpongeBob that in order to cure Gary, he must inject him with Snail Plasma. Because he was too scared to do it himself, most likely because he must have known if you get injected with it you would turn in to a snail. SpongeBob gets injected with it by mistake and turns into a snail. He later appeared in "Suds," where he assigned treatment to SpongeBob when he had the "suds." In "Squid's Day Off," he helped get Mr. Krabs's arms back on him after they fell off. He has a small cameo in "I'm Your Biggest Fanatic" where he does a quick check-up on SpongeBob after Kevin asked him if he wanted to join the jellyspotters. He appears in "Band Geeks", where he mistook Squidward's clarinet playing for a dying animal. In "The Bully," he told Flatts the Flounder that he was in the hospital and that SpongeBob had performed CPR on him for five hours straight. He has a cameo in Mermaid Man and Barnacle Boy IV as one of the citizens SpongeBob has shrunk with Mermaid Man's belt. In "No Weenies Allowed," he recommended that SpongeBob go to the Weenie Hut General Hospital, rather than the hospital he was in, because SpongeBob called his injuries "Boo-Boos." He does not like to be touched by those who have food poisoning, such that Mr. Krabs had in "Born Again Krabs". He performed 20 hour-surgery on SpongeBob's gluteus maximus by repairing it with staples and glue in "I Had an Accident". He made a brief cameo inSquidBob TentaclePants, where he told Martha Smith that she had given birth to a healthy baby, only to have the fused SpongeBob and Squidward to teleport in the baby's place as he shows it to her. In "The Two Faces of Squidward", he performed Squidward's operation. He was paranoid with SpongeBob's interuptions during the final stages of the operation. He is also a dentist, as seen in "Mid-Life Crustacean". He also appears in "Slide Whistle Stooges" where he told SpongeBob and Patrick that the slide whistle on Squidward's throat caused the rescue team to find him. He was then seen doing surgury on Nat Peterson, and laughing with SpongeBob and Patrick when they were playing their slide whistle. When SpongeBob asked Dr. Forrest how Gary could attract all that money in "The Cent of Money", he told him that there was a magnet stuck on Gary's throat, which was able to attract all that money. He also appeared in "Shellback Shenanigans" when he treated Gary (who was actually Plankton in disguise). Forrest also made an appearance in Demolition Doofus while treating Mrs. Puff for a ruptured air sac and tranquilizing Mrs. Puff and SpongeBob.