Aerial bunbardment.

You could actually see the bad idea form in River's eyes just before she pounced like a big cat in a nature documentary.

Bunny optical illusion.

River:  I can totally jump onto that ledge up there!
Simon:  What ledge?  All I see is a closet door.
River:  It's a magic ledge.  If you stare at the door hard enough, the ledge appears.
Simon:  Neat!
(Don't worry, I stopped her before she had a 'hold my carrot' moment.)