Ever see a kid laugh so hard you were actually concerned about his health? If not (and you want to), go see Horn's Punch and Judy Show-it's a perennial highlight among the sub-four-feet set at Artscape and the Fells Point Festival. It's kind of amazing that, in an era when kids are bombarded with Avengers and SpongeBob and Yo Gabba Gabba!, a puppet show that dates back centuries is still the best show in town. Punch and Judy shows have a long pedigree in Maryland, and Professor Horn, aka Mark Walker, has the shtick down to a T, including the thick Baltimore accent, which somehow works in this context. The key, of course, is slapstick. Watching Mr. Punch get snapped in the head by that giant crocodile never gets old. And it never will.