In "Parks and Recreation," Andy Dwyer's karate-themed children's television persona is Johnny Karate.
Andy develops the character late in the series, turning his enthusiasm, silliness, and love of performance into a public-access children's show. The full program is titled "The Johnny Karate Super Awesome Musical Explosion Show," an intentionally over-the-top name that fits Andy's childlike energy.
The character is one of several identities Andy adopts throughout the sitcom. Earlier examples include Burt Macklin, FBI, and the rock-band persona associated with Mouse Rat, but those are not his children's-TV identity. Johnny Karate is specifically the alter ego he uses while hosting his show.
Chris Pratt plays Andy, whose career in the final season expands beyond Pawnee City Hall and into television entertainment. The show-within-the-show also gives Andy a chance to perform songs, teach karate-style moves, and interact with children while remaining recognizably goofy and affectionate.