Lackdork

An individual being excessively silly; who is lacking of intelligence or says stupid things.

That lackdork over there said that two plus two equals twenty two.
I've stopped upon a lackdork, who said that he is a banana.

Bozo

A not-so intelligent or a foolish individual; who is not capable of doing simple things or is being rude and not caring what they are saying/doing.

Look at that bozo.
L (see L) bozo.
Why are you being so bozo?
This bozo said that I look ugly. Which is true :(