CyberToy

CyberToys (also called Robotrons and Convert-a-nauts) are toy robots that can change form, similar to real-world Transformers, but to a more extreme degree. Some of them also have motors, allowing them to move.

CyberToys
Both Arthur and Buster wanted one in the episode "Nerves of Steal." In the episode everybody owned a CyberToy. This caused Buster and Arthur to want the toy like the rest of the kids, so they stole it from Jim's Drug Store. They eventually returned the toy from the feeling of guilt, but they got caught, and Jim called their parents.

It appeared again, although an alternate coloring, as a background prop in "The Long Road Home." It is unknown how Arthur got this one. When wind from Arthur's open window rolled a pen onto it, the toy activated and walked forward, knocking over El Boomerang's box, causing the ball to be lost again.

Convert-a-nauts
A convert-a-naut is a transforming robot that changes from robot mode to a vehicle. It appeared in "Buster and the Daredevils." The name was mentioned by Binky in "Ungifted" when Arthur traded the Thresher for the Bionic Bunny Poster.

Robotrons
Arthur used to have one when he was younger which appeared in Arthur Sells Out, but then sold it to James. It was broken, and James noticed the break in seconds after the sale. Arthur bought him a new Robotron in the end, instead of the video game he wanted.