that's funny
1. That's humorous. A: "So I said, 'What, no ketchup?'" B: "Haha, that's funny. Then what did he say?"
2. That's strange, odd, or unexpected. Huh, that's funny—I could have sworn I turned this off before I left! A: "The computer's not letting me log in." B: "That's funny. Are you sure you put in the right username and password?"
That's funny.
That is strange or peculiar. Bill: Tom just called from Detroit and says he's coming back tomorrow. Mary: That's funny. He's not supposed to. Sue: The sky is turning very gray. Mary: That's funny. There's no bad weather forecast.