What I find interesting about TRANSFORMERS - the original show, that is - is the involvement with comics. Marvel co-developed Transformers with the toy company.
The original proposal for the series was created by Jim Shooter and Dennis O'Neil, after all, at Marvel. The comic itself was written by Marvel editor Bud Budiansky, who created Megatron
He came up with the name Megatron, but that is about it.
Quote from Wiki:
The original Megatron toy was based on the MC-12 Gun Robo, a robot doll released in Japan as part of Takara's Microman line of the late 1970s. The doll was designed to transform from a robot into a model of a Walther P38 handgun.
Pic:
http://en.wikipedia.org/wiki/Image:P-Megatron.jpg