MIB2 had an amazing self-deprecating cameo from Michael Jackson. Marilyn Manson is past his use-by-date, so who else is alien-looking enough for a MIB3 cameo?

Found at a Spanish-language website:
http://elcorillord.com/lady-gaga-actuara-en-men-in-black-3/

Translation from Google Translate:

During the presentation of the film in Rio de Janeiro, to which Smith went with actor Josh Brolin, the former said, smiling: “We have a couple of celebrity cameos, but I think I can not reveal who they are. We must keep as a surprise that Lady Gaga appears. “