When Stuart picks up the bells, he points them at his chest. It then cuts to an over-the-shoulder view, and they are pointed straight up.
Sheldon sings the wrong lyrics on the second verse of "Good King Wenceslas."
When they are playing jingle bells the order on the board is 333 333 35123. Howard is in charge of bells 1 & 2 and plays them in the wrong order 2 then 1.
Sheldon says that the last time he saw Santa, he was at the Baybrook Mall in Galveston, TX. Baybrook Mall is located in Friendswood, TX, located 30 miles from Galveston.
When Sheldon's character casts a paralysis spell on Leonard and Stuart's characters during the Dungeons & Dragons game, he immediately continues describing what his character does afterward, with the assumption that the spell worked. In the game, spells can fail completely, and can also merely fail to affect some of the targets. The dungeon master--in this case Leonard--must roll dice to determine the outcome of the spell, which he does not do. When Howard is the dungeon master in The Love Spell Potential (2013), he performs the rolls for the titular spell.