User blog comment:Kingemocut/Chat bug/@comment-126761-20130508120454

Hi, this was not a hack - this was simply an unusual bug with the chat system (caused by a code inconsistency after the weekly code release) which should now be fixed. The cute kitty just happens to be a default avatar in the system, which it fell back to when the chat servers got confused.

In future, please use Special:Contact for these kinds of reports :) It gets the information straight to the community team for us to review.