Kitty hated taking school pictures. Not only would they not let him do the pose he wanted, but they wouldn't allow him to wear his grill. For the unaware, a grill (also called fronts) is a decorative gold mouthpiece. The kitty version isn't gold, but is rather an extension of the lower teeth, giving a feline an added menacing touch.
Schools don't allow grills in yearbook pictures, citing a correlation to gang activity. The real reason, in my opinion, is that they know the fashion will not stand the test of time, and are trying to save their students from future humiliation.
BUT, schools don't have as much control over the Senior pictures. So now kitty can pose as he wishes, and wear his special kitty grill. Ah, the freedom of burgeoning adulthood.