Robo Power
From Transformers Wiki
A subline of the Activators series of toys for younger children, the Robo Power Activators consisted of a one-step transformation that sufficed for both modes. A large, obviously-colored section was present at the rear of the vehicle mode for each figure, with the section frequently integrated into the overall design of the vehicle. Squeezing the section would cause the toy to transform into robot mode, while squeezing the section again would cause it to transform back into vehicle mode.
The Go-Bots subline of Robo Power has toys which not only have auto-transform mechanisms, but pull-back mechanisms as well.
