Mermaidman and Barnacleboy IV/Doing Time

The first segment here is 'Mermaidman and Barnacleboy IV', which is not so much centered around the superhero parodies named in its title as much as it is mostly involving Spongebob himself. This is probably the more "iconic" of the two 11-minute segments shown here, and it's not hard to see why it's such a classic among 'Spongebob' fans. The entire concept is enjoyably absurd and gets comically out of hand very quickly, leading to a clever conclusion and various hugely successful jokes.
The segment that follows is 'Doing Time', which is slightly less "iconic", but still has many "classic" moments regardless. The beginning of this episode may be the highlight. Seeing Spongebob torture Mrs. Puff w/his godawful driving skills isn't really anything new, but in the opening "action" sequence of sorts it is taken to a whole new level, filled w/creative routes into manic madness and an abundance of hilarious gags that fly at you, one after another, in a triumphantly funny way. Following this great opening is a worthy episode that gets oddly dark and surreal at times and remains consistently hilarious throughout. Plus, the ending is enjoyably inconclusive, playful, unexpected, meta, and fittingly "surreal" in a sense.