Patrick Star is the deuteragonist

Deuteragonist

In literature, the deuteragonist is the second most important character, after the protagonist and before the tritagonist. The deuteragonist may switch from being with or against the protagonist depending on the deuteragonist's own conflict/plot.-History:Greek drama began with simply one actor,...

 of the Nickelodeon

Nickelodeon (TV channel)

Nickelodeon, often simply called Nick and originally named Pinwheel, is an American children's channel owned by MTV Networks, a subsidiary of Viacom International. The channel is primarily aimed at children ages 7–17, with the exception of their weekday morning program block aimed at preschoolers...

 animated comedy series SpongeBob SquarePants

SpongeBob SquarePants

SpongeBob SquarePants is an American animated television series, created by marine biologist and animator Stephen Hillenburg. Much of the series centers on the exploits and adventures of the title character and his various friends in the underwater city of "Bikini Bottom"...

, created by creator Stephen Hillenburg

Stephen Hillenburg

Stephen McDannell Hillenburg is an American animator, writer, producer, actor, voice actor, and director best known for creating the animated series SpongeBob SquarePants. He currently owns his own production company, United Plankton Pictures...

 and voiced by Bill Fagerbakke

Bill Fagerbakke

William Mark "Bill" Fagerbakke is an American actor and voice actor. He is well-known for his long-running-roles as Patrick Star in the animated series SpongeBob SquarePants and "Dauber" Dybinski on the sitcom Coach....

. Patrick's most significant character trait is his lack of common sense, which sometimes makes him a negative influence on his best friend, SpongeBob SquarePants

SpongeBob SquarePants (character)

SpongeBob SquarePants is a main fictional character in the animated television series SpongeBob SquarePants. He is voiced by Tom Kenny and first appeared on television in the series' pilot episode "Help Wanted" on May 1, 1999. SpongeBob was created and designed by cartoonist Stephen Hillenburg...

. Patrick is the third most recurring character on the show, appearing in 253 episodes, behind Squidward's 270 and SpongeBob's 305, although he is more well-known than Squidward.
Patrick is portrayed as fat, lazy, unmannered, dimwitted, and generally ignorant.