Mirror is the combined form of the Mini-Cons Rook and Crosswise, the partners of the enigmatic Sideways. Little is known about this tiny combiner's personality or abilities, as he is generally seen only as a passenger for the treacherous bulk's vehicle mode, generally separating when his master transforms so that one of his halves can form Sideways's head.

In his debut episode, Gale, he uses a disguaise to appear more like a motorcyclist. His head looks like a helmet, which is revealed to be a hologram. His body is covered in a leather outfit, which is later revealed to fold into Crosswise's Powerlinx port, or the equivalent of a belt buckle on Mirror. This disguise is oddly never used again, which is a stupid decision. Because let's face it, in his normal form, he makes Sideways look even more suspicious (when's the last time YOU saw a robot riding a bike?).
He has no official English-language name, the closest he has being "Twins", as Sideways was originally solicited as "Sideways with Twins" rather than "Sideways with Rook and Crosswise". Thus, one could consider him this decade's equivalent of Bumper.