Acronym for "WHO THE HELL DO YOU THINK I AM", a catchphrase from the anime Tengen Toppa Gurren Lagann. Said a gratuitous number of times by Kamina, Simon, Kittan....okay, EVERYONE in the whole d-mn series. This is a common abbreviation used on social networking sites (okay, and 4chan) to condense the phrase.

Internet persona(s) who happens to follow you and you happen to follow them back and maintain communication with and have a mutual liking for eachother whether it be friendship wise, etc. (Mutuals if more than one mutual)