"I'm a lunatic!"

My sister Becky has taken up a strange new catchphrase. She often walks around the house saying, "I'm a lunatic! Come on, say it with me!" I don't know where she made this up. I have a feeling that I may have influenced it in some way, shape or form, but I never actually said it. It has led to much bemusement on the parts of everyone who lives with her (i.e. me, Mum and Dad).

Mum was interrogating her a bit on this matter today.

Mum: "Who says that?" (thinking it's from a cartoon or movie or something)
Becky: "Me!"
Mum: "Who made it up?"
Becky: "I did!"
Mum: "*laughs* You know, I think it's funny. Not the 'I'm a lunatic part', because I actually don't like it all that much. But it's the 'come on say it with me' that I think it hilarious!"
Becky: "Come on, say it with me!"

That's pretty much how it's been for us.