When my bunny was a baby, he had both ears straight up, but within the first couple weeks, one flopped over. He's full grown and everything now, but I am just wondering what may have caused it. I know nothing is wrong (and it gives him personality), but I am curious about it. Anyone else have a bun with the same thing?

Before and after:

We call them "helicopter ears" when one is up and one is down.

From a slightly different angle- a friend has 2 bunnies from the same litter of lops and they both have ears that are upright- is that common?! they must be around 12 weeks-ish old now. i guess if they were kids they'd be the ones being picked on- "call yourself a lop? yer'v got sticky-up ears you have..."! 

First - CUTE!!!

It is normal for a bunny to carry on characteristics from parents and grandparents, so you'd have to know the bunnies family tree to find out where the upright or floppy ear came from. And so unless there was some injury, which you'd know, as your bunny would be in pain, this is normal.

and loopy-lop, their ears may flop down eventually, or they just had some parent or grandparent with upright ears.