"Wizard of Oz" joke

Wizard:I am the wizard of Oz! Why have you come here?
Scarecrow:I have come for my brains!
POOF!
Wizard:You are now the smartest person in all the land!
Scarecrow:2 times the square root of 4 squared is equal to 2 plus 2!
Others:What does that mean?
Scarecrow jumps and lands but...
Scarecrow:Ouch! It means I landed on my nose!