It is a large, heart-shaped balloon that is brown due to it being filled with chocolate. It also has a poorly drawn image of Patrick in the middle.
Role in episode
The chocolate balloon is Patrick's Valentine's Day gift from SpongeBob, who has Sandy arrive at the Valentine's Day Carnival later with the balloon to surprise Patrick with it. Unfortunately, the plans are ruined when chocolate-eating scallops start to fly at the balloon, causing Sandy to delay her arrival. This eventually results in Patrick going mad and causing trouble at the carnival, believing SpongeBob did not get him a gift.
Fortunately, Sandy arrives, and SpongeBob (and the other Bikini Bottomites) try to convince him to turn around, but Patrick stubbornly refuses. However, after hearing Sandy greet him, Patrick turns around and sees his gift. Patrick excitedly hops toward the chocolate balloon, but it bursts upon Patrick biting into it, releasing chocolate that explodes all over the carnival.
Patrick does not get enraged at this, for he is delighted that Spongebob attempted to bring him a gift. A pleased Patrick tells SpongeBob that he did not have to get him anything despite what he did at the carnival.