It's Arbor Day, Charlie Brown is the 15th prime-time animated television special based on Charles M. Schulz's comic strip Peanuts. The subject of the special is Arbor Day, a secular holiday devoted to planting trees. It's Arbor Day, Charlie Brown premiered on the CBS network on March 16, 1976, which is near the dates in which most U.S. states observe Arbor Day. This is the first special to feature the character Rerun van Pelt (younger brother to Linus and Lucy), who had debuted in the Peanuts comic strip in March 1973.