"Thundersmall" is an episode of Special Agent Oso. It's also the series finale.
Dotty trains Oso to jump his car off a dock onto Wolfie's submarine, but--as always--Oso fails in his training exercise on his first try. After all, Oso is a special agent in training. Meanwhile, Professor Buffo has invented a new machine that shrinks things. After he tests the shrinking machine on Wolfie's motorcycle, Oso plays with it, thinking it a toy. Suddenly, Oso, Dotty, Wolfie, Professor Buffo and Whirlybird accidentally get shrunken by the invention, and chaos breaks out in the U.N.I.Q.U.E. Dome. Now it's up to Oso to find a way to save himself and his friends in order to return to normal size, and he will find what it takes to become a real special agent.