An asinine bunny, where else?
Way back in the early history of photography, back when people had metal rods strapped to their backs and clamped to their necks so they could sit still for the 30 minutes required for exposure, there were no bunny ears. In fact, in those portraits, there were no smiles. It was a very severe time, as though everyone had just received terrible news... It is impossible to pinpoint exactly when bunny ears first showed up in photographs behind someone’s head, though it started happening often in the ’50s. And, oh, to know why they did. ... Why a rabbit? Why not a Statue of Liberty crown with all five fingers? Why not a single antenna? Why not devil horns, with the index finger and pinkie?
We can't assume that the prank only came into existence when people started to pose for photographs. Nowadays it's rare for someone to make bunny ears except when a photo is being taken. Though maybe, back in the middle ages, making bunny ears during formal occasions (perhaps as the priest was saying mass) was a popular jest. Who knows? Obviously this is a subject crying out for further research.
I have no idea, but whenever a picture is taken of me and my siblings, I always end up with them.