Baby Bop is sad because she lost her pet caterpillar, Monty. Barney and the others try to help her find it. Baby Bop is surprised to discover Monty inside a chrysalis. Everyone is excited to find Monty — now a beautiful butterfly! Barney and Baby Bop are thrilled when BJ sets up a bug zoo in the caboose, but Riff isn’t so sure he wants to be around bugs. When the park is magically transformed into a amphitheatre with insects performing, Riff discovers that bugs don’t bug him after all.