Which two animals can stand on their heads?

It is impossible. Ever tried putting your feet on your head. How about standing on somebody elses head. Humans and Apes all have the ability to do the misnomer of what we recognise 'as standing on their heads'. I have also seen elephants do it in the circus. If an ostrich buries its head in the sand could that be classed as standing on it's head?

I have seen a circus performer put her feet onto her head - can't say flat because the skull isn't flat, but she put her feet flush to her skull, at least. Watch Blue Peter, you'll see this kind of thing three or four times a year.

Hmm... None! Skunks perform handstands when confronted by a predator, altough this is not of course standing on their head... Humans can stand on their heads (Does that count?) but no animals apart from humans can actually do this.