...has anyone ever told you two you act like one of those old married couples?

[She wasn't directly implying that they were together. But only because she didn't need to. Bart's words and actions, combined with Tim's reactions, were more than enough for a strong insinuation to hang in the air.]

[Whether or not it was actually true didn't even matter. Because it was funny, and that's what did matter.]

What's the whole deal with this Mr. Sarcastic thing you keep bringing up, by the way?