"I can't believe you've gotten so big in just six months."
It's not as bad as it sounds because she was talking to my daughter who really is sprouting.
I thought about a couple of other things you could say, but just not to everyone.
"I'm going to beat you!" When I play checkers with my son.
"I'm not speaking to you for the rest of the year!" When said on December 31st at 11:59.
"You've got a really nice ass." When spoken to a person who raises donkeys.