After a night dancing, Amy kisses Sheldon. It's their first kiss!
Sheldon makes a grave mistake in this scene: he drinks from Leonard's glass!

The Big Bang Theory Season 4 Episode 23 Quotes

Sheldon: Do you know where the phrase jibber jabber comes from?
Penny: Oh my god, you're about to jibber jabber about "jibber jabber?"

Have you told your parents you're dating this short glass of skim milk?