Hop on the Magic School Bus for a Visit to Herp Haven and a journey back in time.

The class discovers that Liz is missing, gone off to a mysterious place called 'Herp Haven'. Why has she left them? Thinking she's in trouble, they rush to Herp Haven, where they are transformed into reptiles in order to get past Mr Herpst, the proprietor. Now reptilian, the class finds out what it means to be 'cold-blooded'.

Ms. Frizzle takes the class to a dinosaur dig, courtesy of her old school chum, archeologist Dr. Carmina Skeledon, and then decides to complete this field trip by travelling back in time 67 million years to see what dinosaurs are really like! Arnold squares off with a T-Rex, and the class finds out, to their relief, that even the fiercest dinosaur prefers flight to fight.