One of the most interesting pieces of box office [1] news this past weekend was the Labor Day sales bump [2] for Mamma Mia! [3]. The movie was in its seventh week in theaters, but it actually saw its sales go up after several weeks of drops. Getting most of the credit: special sing-along screenings in almost 300 theaters, which alone brought in $1.2 million over the long weekend. Hey, I can understand — who hasn't belted a cheesy ABBA tune or two in their day?

Of course, Mamma Mia! is just the latest in a tradition of sing-along screenings. Hairspray [4] held some sing-along events, there was a popular Buffy the Vampire Slayer [5] sing-along (until it got itself in trouble with Fox), and of course there's the king of all sing-alongs, The Rocky Horror Picture Show [6]. Heck, even R. Kelly's Trapped in the Closet got some sing-alongs earlier this year. So I'm wondering: Have you ever been to one of these events? Tell me your stories in the comments!

Photo courtesy of Universal Pictures [7]