Cass's very shy, humble Heel Realization at the end of Dorkness Rising certainly qualifies.
Though it's mostly a humorous moment, there is kind of a heartwarmingness when Lodge makes Sir Osric go "examine the architecture" when the rest want to torture the demon. Lodge finally takes Joanna's advice and lets go of his storytelling and lets them play the game.
In Hands of Fate, after Cass's deck is burned by The Legacy, the crowd at the finals all band together and loan Cass their cards so he can rebuild his deck from scratch. The final card, The Apple of Life, is given to Cass by Natalie.
After Cass's breakdown, the mood is very awkward until Gary moves next to Joanna and asks, "So... What happens next," showing that while Cass's attitude towards the story may not have changed, everyone else became very invested. Joanna gives him a small smile out of thanks.
Lodge and Joanna's True Dungeon scene (only in the extended edition).