It never ends.
He couldn't see it coming
Hit it in the face with an axe.
He got hit by a bus
A snooker table
Found on /r/linux) A: Open the other end
An envelope!
You have to drop da bomb on her twice
Nobody asks, 'who's there ' when you try and tell a knock knock joke.
Student: Depending on what pie. Usually is $12.99
Because he kept throwing his pi in other peoples faces!