The Funky Phantom S01 E11 Pigskin Predicament

The kids return to their high school for the big ball game (""You two are players, I'm the cheerleader, and Elmo's the mascot""). Two robbers steal a rich lady's necklace, and hide in the football, they disguise themselves as players to get the necklace back. Naturally, they're found out, and arrested.