Character model
A Character Model refers to a character's in-fiction appearance (as opposed to their toy.)
Character models can be radicly different from their toy (example: Ratchet.)
Sometimes the same toy is understood to have radicly different appearances, as in the case of Red Alert and Sideswipe. (see illustration at right) These two toys are essentialy identical, but one characteri shsort and stocky, the other tall and athletic. Despite being based on the same toy, they do not 'look' the same.
Hot Rod is notable for having two different character models based on the exact same toy, mold, colors, etc. The 1986 toy represents his lithe from in Transfomers:The Movie. That same toy, re-released in 2001, represents his smaller, bulkier form as "Rodimus Major" in the Beast Machines era.

