Britney Spears has filed for divorce from Kevin Federline, claiming irreconcilable differences, though we thought the two could not have seemed more alike or suited to each other. We are sad for Federline. Apparently, Spears had already filed when she made her “surprise” appearance on Letterman last night (complete with Paul’s Bob Hope-surprise-walk-on theme accompanying her entrance), though the only thing surprising about it was her head-to-toe renovation after that mess we saw with Matt Lauer. She saved the real surprise for today. The pop world may be heaving a huge sigh of relief, but we’re still sad. Details on the divorce here and here, and Letterman footage here.