Convert-o-naut

Convert-o-nauts are toy robots that can change form into vehicles.

It is not named, but the transforming toy Arthur plays with at the store in "Arthur Bounces Back" has a similar function to Convert-a-nauts.

Though again not named, Arthur and Buster each own a Convert-o-naut, which appeared in "Buster and the Daredevils." Brain also owns a special version (called "Brainbot" by Buster) that can "transform into anything".

The name was also mentioned by Binky in "Ungifted" when Arthur traded the Thresher for the Bionic Bunny poster. They may be a parody to Transformers.