Presumably it was because of the new PB song ‘BATMAN’.
He also posted Jack Nicholson as Joker (which for some reason I can’t find now) and a terrible Batman logo rotating gif.
Revisiting his Instagram, that dog is so unbelievably ugly. It saddens me to think that this creature was bred specifically to not only look that way but also to have lifelong disabilities (brachycephaly etc). Dog eugenics for toy breeds is so messed up.