But death is a series by tenagedpanda and pasteljirachi (currently unknown people) of other characters singing the Rocket Monkeys Theme. There are only two parts so far.
dib but death[]
It starts with the classic "The Rocket Monkeys, the monkeys in space" as the character one screen, Dib from Invader Zim, is bopping along with it. During the "oh you rocket monkeys" part, there is a collage of "slumbiuses" (what pasteljirachi calls them).
The sentence "please let me die rocket monkeys is horrible" is used in the Notes, implying that pasteljirachi hates the show (I mean, who doesn't?).
Sig but death (Test)[]
In this one, it uses an different animation style (DBD used puppeting, while SBD uses tweening) and a different character, which is Sig from the franchise Puyo Puyo. It's shorter than DBD, only including the first verse. However, tenagedpanda has told pasteljirachi that they are making an extended version