How to be an idiot - Part I:

1) Run into girl you have crush on going up the stairs.
2) Ask her brightly how her dog is doing.
3) Notice that she is staring at you like you have something between your teeth -- When she responds [oh, so politely] with: "You mean Emma's dog?" realize you have her mixed up with another girl you were hitting on yesterday, lower your eyes, mumble something stupid and rush away from her down the stairs.

Doh!