Radius Ulna "R. U." Humerus (Tony Randall) is a one-time character who appeared in "Flexes Its Muscles". He also hosted its producer segment. He is Professor Frizzle's mechanic and an expert on the MagicWare of the Magic School Bus. In the episode, he provides M.I.K.E. to Ralphie and helps him build the Ralphiebot. He insists on being called R.U., and he appears to have some romantic attachment to Professor Frizzle; throughout the episode, the two are seen teasing and mildly flirting with each other. After Ralphiebot was destroyed, R. U. later rebuilt it. He now works with it Lizbot.
Trivia[]
- According to a Carlos gag in "Flexes Its Muscles", his name is a pun on "Are you humo(u)rous?" and the radius, ulna, and humerus (the three bones of the arm).
- He appears in a cameo on a painting in the Frizzle sisters' house in "Gets Charged".
| Parents | Mr. Perlstein | Mrs. Perlstein | Mr. Hudson | Mrs. Hudson | Mr. Ramon | Mrs. Franklin | Mr. Terese | Dr. Tennelli | Mrs. Li |
|---|---|
| Siblings/Cousins | Murph* | Evan Hudson | |
| Friends | Professor Cornelia C. Contralto II* | R.U. Humerus* | Dr. Skeledon* | Molly Cule* | |
| Pets | Wanda's Dog* | Noodles |
| Other Characters | Mr. Seedplot* | The Baker* | Mr. Junkett* | Harry Herp* | Gerri Poveri** | |