Conversation with 3-year-old son at the zoo yesterday

HIM: Daddy, what comes after birds?
ME: Birds?
HIM: Yeah. What comes after them?
ME: Where...uh...what birds do you mean?
HIM: Birds! Birds in the sky! Birds!
ME: Oh. Right. Birds.
HIM: What comes after them?
ME: Oh. (pause) I don't know.
HIM: Do you want to be a family of wallabies?
ME: Yeah, okay.