DESCRIPTION
Sully is ticklish, and Mathilde loves utilizing this weakness to get him to notice her, and perhaps even get him playfully mad at her.
On a lore note, Sullivan's wolf form isn't fully dependent on the phases of the moon, but his emotions. It tends to come out on its own during moments of extreme excitement, anger, fear, or in times of danger. Sometimes, when the emotion is strong but brief, just his ears, tail...or another thing he doesn't normally have will pop out.