It's a match made in "Hills" heaven! High school sweethearts/reality stars, Doug Reinhardt and Allie Lutz are engaged, the blonde bride-to-be announced via Instagram on Sunday. "Cat's out of the bag," the 26 posted along with a picture that showed off her massive ring and Doug giving her a sweet kiss on the head. You may remember Allie from the last season of "The Hills," she appeared on a few episodes of the show as one of Kristin Cavallari's old high school rivals. Reinhardt, 28, had a longer spot on the MTV series and briefly dated his "Hills" costar Lauren Conrad in 2008. Doug's also been romantically linked with Amanda Bynes, Cassie Scerbo and Paris Hilton. Doug also played baseball for the Los Angeles Anaheim Angels and the Baltimore Orioles. Congrats to the happy couple -- click "Launch Gallery" above to see even more celebrity engagement bling! Read more...