It was a yellow metalic bipedal robot that looked similar in appearance to SpongeBob except for lightbulb eyes, a metal bolt for a nose, a frowning mouth with glowing teeth, and a tail pipe behind him. One of the largest differences between SpongeBob and Robot SpongeBob is that Robot SpongeBob has a transparent glass container on his head, that is filled with fluids and can hold SpongeBob's Brain so that Plankton can get a Krabby Patty. Robot SpongeBob also has one arm that looks like a Spatula and another that is a metal pincer.
Robot SpongeBob was a robot created by Plankton to force SpongeBob in to making a Krabby Patty, and is confirmed as Plan B. A few months after Plankton had failed to get win the card games he played with Mr. Krabs to get the secret Krabby Patty formula, he had finally won the card game (after cheating) and had then won SpongeBob's contract so he could work at the Chum Bucket. SpongeBob did not have the proper ingredients to cook a Krabby Patty, but he was to be treated with compassion and understanding. Later, SpongeBob became less disciplined, and called Plankton a bad name. Plankton took out his brain and put it into the Robot SpongeBob, Plankton programmed the robot to make a Krabby Patty, but then Robot SpongeBob said: Response: Why don't you ask me later?'Then Plankton yelled at him to follow his orders, but Robot SpongeBob said 'I don't wanna' and lazily drank gas soda while reading a comic book that had a comic strip of SpongeBob, and Patrick, and Squidward. Personality-wise, Robot SpongeBob is shown to be sassy and does not follow Plankton's orders to make him a Krabby Patty replying with "I don't feel like it". The robot had that response because it was still SpongeBob's brain, which has his personality, thoughts, and memories in it. Plankton just gave the brain a new body to maintain the brain which ultimately back fired which doesn't change that SpongeBob is taking advantage of Plankton. It is also shown he likes to drink oil and read comic books. Plankton becomes frustrated and puts the brain back into SpongeBob, himself. He also appears in the PC version of The SpongeBob SquarePants Movie (video game) where Plankton must distract him to grab the jetpack without being crushed. Later, SpongeBob must avoid being seen by him in a maze while grabbing Krabby Patties.
The premise of Robot SpongeBob is similar to The Simpsons' Treehouse of Horror II segment featuring Homer's nightmare. Homer, a lazy worker, is kidnapped by Mr. Burns and Smithers, who put his brain into a robot. The robot ends up being lazy and refusing to work, just like Homer.
Part of the control panel of Glove World in "Tunnel of Glove" looks just like the robot.
The robot is an obvious parody of Frankenstein's Monster, because in the book/movie Dr. Frankenstein puts corpse body parts to make the monster come to life, as in here SpongeBob's brain is transferred into the robot.