The Butterfly with laser gun appears in "The Other Tarts." He robs Finn and Jake of the last two royal tarts as they are traveling through the Desert of Doom. After he threatens them and shoots at them with his laser gun he flies away with the tart container, saying he has to "book it to Nana's for brunch." He is last seen gliding through the air, his body paralyzed after having taken a bite of the unintentionally poisoned tart. He seems to be very strong because he is able to lift an Anti-gravity tote chamber, despite his small size.
This is the first butterfly in the series that can speak.
His appearance in the model sheet is different from his appearance in the actual episode. On the model sheet, he has a different belt, larger head size, thicker antennae, and eight legs, while he only had two in the episode.