It’s a miracle on 42nd Street. The long-unseen Christmas episode of WPIX/Ch. 11’s beloved “Magic Garden” children series has magically reappeared and will air Christmas Day at 6 p.m. “We’re beyond excited,” says Rolando Pujol, executive producer of digital, who along with licensing producer Joan De Jesus discovered the show in a forgotten sub-basement at the station’s East 42nd St. offices earlier this year. The show originally aired on Dec. 13, 1981. It may have had a re-airing a year or two later, but then it disappeared. It turned up among several hundred vintage WPIX tapes in a long-ignored room,...