Gus's baby sister Tilly is a nuisance. She destroys Gus's room, she steals his cookies, and basically makes his life a mess! But is Tilly a mutant? Gus sure thinks so, and he's called the mutant experts in to find out for sure! Will the X-Men discover the truth about Tilly ... or will Gus be too annoying for them to even care?
— Description from Comic Vine community (comicvine.gamespot.com).
