Dennis the Menace - S01EP16 It's a Ruff Life/Professor Myron Mentalapse/Dennis Race 2000

When Ruff upsets one of PeeBee's experiments, the dog and Joey end up with their brains switched, Ruff can speak, while Joey can only bark! PeeBee and Dennis chase them around town, trying to capture them and re-switch their brains back to their owners. The kids meet a looney Professor at the Science museum who has built a time machine that is ever so close to actually working. When their teacher tells the kids that they must have a science project turned in the next day, Dennis gets the wild idea of going back in time and taking actual photographs of actual dinosaurs. They're wild idea is made possible when PeeBee reworks the Professor's calculations and makes the time machine work! WHOOSH! They go back to the prehistoric age. While they befriend a baby dinosaur, the problem is that the time machine is sinking in quicksand and the mother dinosaur is chasing our heroes! Fortunately Dennis and the kids are able to retrieve the time machine and return home with the photos... unfortunately, they contain NO dinosaurs!. Dennis challenges Margaret to a soap box race, building a homemade car with Joey's help... and loses.