The letter "m."
A) I don't know he also stole my watch.
There's no punch line.
It depends on what side of the bathroom door you're on.
Ask him what color the blue line is and wait. It may take him ten minutes to answer.
He gets Tenyear.
A decade Ba dum tish.
A Pair-a-ducks.
The letter M
Because it turns "ice" into "mice"!