If You're Happy And You Know It...

Keep it to yourself.  And definitely no clapping of hands. 

How about "If you're in a pissy mood and you know it - take it out on other people."  Or

"If you're dirty and you know it - take a shower."  Or

"If you're a cat and you know it - meow."  Sing along with me.

"If you're stupid and you know it - you probably don't because you're stupid."  Or

"If you're an actor and you know it - you probably live in LA."  And finally because it's Friday and I'm tapped out...

"If you're rich and you know it - send me money."