They started out as Nissan Onebox Cherry Vanettes. The original Diaclone toys were non-sentient beings and were meant to be driven by humans. You can tell because they have seats, but no robot faces. (The cheapo cop-out sticker for the face was an addition by Hasbro.) Fun fact: Bob Budiansky, the writer from Marvel comics who was reponsible for the Transformers backstory, said that Ratchet was named after Nurse Ratched from One Flew Over the Cuckoo’s Nest. I KNEW IT!
As almost a nod to history, the new toys for the Transformers movie are based on the same GM Truck platform: Ironhide being the GMC Topkick and Ratchet being the Hummer H2. However, they transform into two distinct robots. I love how their panels pop-out. In older transformers, the design philosophy was more towards folding large masses of plastic or metal. In these toys, the panels pop into pegs and collapse on each other, reminiscent of how the transformations happen in the movie. Michael Bay mentioned that he wanted to stick to bulkier vehicles to make the transformations seem realistic, and I think he was right: everytime I see a massive SUV (especially painted in a bright neon color), I try to imagine what I would need to do to turn that vehicle into a transformer.
I hear complaints among Transformers fans that Ratchet looks “Playskool”; that is, that the toy looks like he’s design for children. Well, I say SCREW Y’ALL. He’s actually painted like a real rescue vehicle, and some people happen to like lime green.