At this year's Teacherathalon, Ms. Frizzle is competing against Mr. Sinew, the gym teacher with giant muscles. Janet (from Gets Lost in Space, Butterfly And The Bog Beast, Gets A Bright Idea, and Goes Upstream) shows up again and supports Mr. Sinew (Dan Marino). The class is convinced that there is no way Ms. Frizzle can beat someone who can destroy shirts simply by flexing his muscles. Ralphie wants to know what lungs have to do with how your muscles work, so they go on a field trip inside the Friz herself.