Santa

Santa is one of the boys' greatest allies and a major protagonist who has consistently been a primary force of good since the series premiere.

First Ball Strike
Santa was subject to a devastating blow to the balls by Joey from gym class and was subsequently changed forever.

Second Ball Strike
Santa was subject to yet another strike to his groin by Joey from gym class and was only able to hang on to his life through the recovering powers of Chaeyoon's Call of Mommy.

It is revealed later in season 4 that Joey was using the ball strikes to steal Santa's height and grew an entire foot as a result of the Ball Strikes. This explains why Santa was weakened and susceptible to becoming his Sicko form throughout the series.

Trivia

 * Thanks to Santa's mic, all the boys are now nearly fluent in mumbled radio buzzing