Patrick SmartPants is a more intelligent version of Patrick, with interest in science and music. He is less interested in the "unintelligent" hobbies that the normal Patrick would do, like going jellyfishing.
Role in episode
Patrick SmartPants has emerged when normal Patrick's head has been accidentally cut off by smashing through a wall as a result of falling from a cliff. SpongeBob then screws in the "smart" head into Patrick, thinking it was Patrick's original head. The "smart" head accidentally forms Patrick SmartPants. He then acts intelligent for the rest of the episode. Everyone thinks the original Patrick got amnesia and sounded terrible.
Further, towards the episode, Patrick SmartPants does not like how his friends treat him and misses his old friends' interaction with him. After he attempts to have fun the way he used to, it fails and he sees he needed to return to his old self. Patrick SmartPants jumps off a cliff to repeat his previous accident.
Afterwards, he is shown to still be smart but realizes that he needs to find his old head once he sees SpongeBob mistakenly grabbed something else. He finds his real head and the source of his intelligence is revealed to be brain coral. Patrick SmartPants says that would rather sacrifice intelligence so that he can have friendship, so he takes out his "smart" head and SpongeBob puts Patrick's old head back on. From there on, Patrick SmartPants becomes the normal Patrick once again.