Here is the Megatron Megabolt that came out of the Robots In Disguise line.
Here is unproduced original Megatron Megabolt prototype.
The basic idea is the same as the production model (in that they're both transforming head/space crafts), but is essentially a completely different toy. It's actually easier to note the similarities between the two designs. Basic shape and certain areas of transformation are akin, but like the cartoon; does not have the legs. Instead the original jet thrusters adorn the underside of the prototype. Interestingly though, the lower jaw of the production version more closely resembles the cartoon.
A comparison shot of the two toys.
Robot mode images
Not to gloss over the below debut robot mode images but the most incredible feature of this concept is the working mechanism visible through the clear sections. When the eyebrow/chest section opens up, a series of cogs engage and actually move within the prototype giving a true mechanical effect.
For the full story behind this piece of Transformers history, check out the Robotpoints blog.
