As fractures go, a buckle fracture sounds like the best kind to have. The bone is compressed on one side, so it warps slightly, but no parts actually break off. Buckle fractures are common in kids and heal up fairly quickly. Four weeks is a long time for a three-year-old to be in a cast. At least, unlike Conrad, I'll be able to console myself that it could have been longer. It could have been worse in any number of ways. We're lucky to get to spend Christmas, In-laws-mas, and New Year's wrestling a forearm cast through the safety straps of the car seat and stroller.
The Buster-Keaton-worthy comedy part is the same as the heartrending part: the cast is so heavy, every time Conrad runs, his own swinging arm pulls him off balance. Sometimes he lands on his tush and giggles. Sometimes he face-plants and wails. If only this were happening to a cartoon character, it would be a guilt-free hilarious running gag.
Really, the whole thing would be way better if it were happening to cartoon characters. In the movie of my life, I'd like to be voice-acted by Mel Blanc. Don't worry, he could voice-act your part, too.