Banette asked for a donor bar, so I made a small one on top of the poster. If it becomes a problem, go ahead and delete it.
According to what I was told, you have to rocket jump up to it, walk along the poster and into the donor bar.
Most of the bosses have no way to get to the player in the bar, or to kill said player(s) in the bar.
EDIT 2: He just removed it, never mind.
EDIT: I'm also wondering what exactly this "rainbow floor" is, was also told that just now as well.