I used to do this when I was a kid, but the interchangeability on Pretenders varies. Some can change shells better than others, because the shells are essentially form-fitted to the individual robot. Some make it difficult to close the shell halves while others fit in snugly. So it's not quite as universally interchangeable as the Headmaster, Targetmaster and Powermaster gimmicks; those gimmicks were intended to be interchangeable ("Cross Head On!") whereas if any Pretender can fit in another's shell, it's more of a happy accident.![]()