I'm bored! (As in board) Another one from my 9 year-old.
3, duh. (My ex's 9 year old little sister told me this joke, and followed is up with: "and YOU'RE the math guy!" >< Burned.)
Echosystems. From my 9 year-old.
A: They are the only ones who erase their notebook when the teacher erases the board.
Whenever he boards a plane it neverlands