That the Ying Yang Twins have returned with a song called “Big Butts” is not surprising. In their heyday, the Atlanta duo reliably pumped out radio-rap songs that could easily be mistaken for well-produced, if ultimately uninspired, parodies of radio-rap songs: “Get Low,” “Salt Shaker,” “Shake,” and, best of all, the male-exhibition-advocacy banger “Wait (The Whisper Song).” (That one actually got a pretty great parody, via the early Lonely Island). “Big Butts” is a breezy extension of the brand: The Ying Yang Twins like big butts, they like the sound of the big butts smacking against the ground, they like when girls make their big butts go “wompdy womp,” etc. The video’s actually fairly tame, with a Pop-Up Video-style speech bubbles literally reading “Big Butts” covering all big butts. But that’s not the big surprise here. The big surprise is: “All proceeds benefit The Ying Yang Twins USAFE Project to benefit HIV/AIDS prevention and education.” Wait, seriously? Yes, seriously. According to its promo material, USAFE “is the brain child of the Ying Yang Twins, in honor of [group member D-Roc’s] little brother Corey Holmes, who passed of AIDS at the young age of 25.” Add the Twins, “It would be unfair of us to tell fans how fun sex is and not tell them how dangerous it is as well!” Well, there’s not really much we can add there. That’s just commendable. Thanks, Ying Yang Twins!