Ultimate X-Men Annual #2 (2006)

Breaking Point / Why Xavier's Cat Is Named "Mystique"
"Breaking Point" - Dazzler awakens from her coma to have Kurt whisk her away to a secret cave where he goes to think. He tells her the X-Men have been attacked, and that they need to lay low until the Professor contacts them to say the coast is clear. Meanwhile, the X-Men, who haven't been attacked, are informed about Dazzler's disappearance. "Why Xavier's Cat Is Named 'Mystique'" - This two page bonus feature reveals why Emma Frost named Xavier's cat "Mystique."
Release Date: 2006