S2·E18 Why the Baboon's Balloon Went Ka-Boom!

Theo wants to teach the cubs a lesson, which he finds in a book of concatenations called Because a Little Bug Went KA-CHOO! What Theo doesn't know is that, by pulling that book from the middle of a pile, a pen dropped to the floor, setting off a concatenation in the library. It culminates with a hot-air balloon's bursting.