It's a bit lost in translation I guess (and maybe explaining the joke kind of ruins it), but this kind of humor is more often found on the Japanese reality TV and improv scene. I'm not sure there's a name for it. The idea was just simply the odd one out—the straightman, usually the only sane person in the midst of the fools, gets treated as the weird one because everyone is a fool.
It's kind of a twist from the typical manzai format. While the audience is usually expected to empathize with the tsukkomi because they share the same 'normal' sensibilities as the audience—treating the boke as the freak—this flips that upside down by treating the boke as the normal instead.
In reality TV, this joke usually ends with the boke chastising the tsukkomi for being 'weird', unaware of the irony. Alternatively, like in this comic, they up the weirdness to further push that the 'weird' was really the normal in that gag's world and the sensible one was the fool.
