You Don't Make Sense To Me : Part 2 : Megatron

From the universe of Transformers comes Megatron, one of the characters that really doesn't make sense. Here's a robot several stories high with lots of mass and weight and yet is able to transform into a light weight handgun. Where does all the mass and weight go to ? Better still, in the entire history of the Transformers why doesn't the Autobots just stomp on him while he's in handgun mode ? Megatron... You Don't Make Sense To Me..