The joke is a pun with a triple meaning of the word change. Transformers are robot characters from a television series called Transformers. They change forms from a giant robot into inconspicuous vehicles. Change also refers to coins. Change could also refer to structural change in the way problems are handled in a government or society, which is what "being a big fan of change" sometimes means. The transformer, probably an autobot, is a good guy who carries coins in his pocket because he's a big fan of change.
The Transformer always had a lot of quarters with him . He was a big fan of change .