Orange you glad I didn't say banana?

Completely random, non-TV-related post for the day: my almost five-year-old daughter is obsessed with knock-knock jokes (she's laughing right now as she reads the subject line over my shoulder), and I'm running out of good ones that are age-appropriate in terms of both taste and her ability to understand them. You people seem both smart and funny (and occasionally juvenile like me), so I figured I'd ask for suggestions. Knock away.