S2·E42 Simon Says.. No Thanksgiving, Part 2

The next morning, the pair are stopped by a cop as they head for the street corner to push the buttons on the tricky control box. The cop tells them that it is Thanksgiving Day and the parade will be marching down the streets for hours. Hence, no one is permitted to cross the streets. This doesn't stop Simon. Together, the two villains head back to Simon's basement lab where Simon takes out one of his time bombs. The evil twosome will travel back in time to prevent the Pilgrims of 1621 Plymouth Rock from becoming friendly with the Indians and starting the Thanksgiving tradition. But the two villains are unaware that Sweet Polly Purebred has been following them and she calls for Underdog for help. Sweet Polly and Underdog head for the two villains' basement lab where they find Simon's hidden cache of time bombs in a secret compartment behind a bookcase.