David Letterman is actually going to appear on someone else's show. He'll be the first guest to welcome Regis Philbin back to television when he returns this Thursday.

Reeg has been recovering from triple-bypass heart surgery for the last six weeks. Dave and Regis have always had some weird, sort-of love/hate relationship. When Dave has his own heart bypass surgery in 2000, Regis stepped in several times to host for him. Regis did the same when Letterman was out with the shingles in 2003.

Dave didn't step in to host with Regis, but that's probably a good thing because I think Dave would've killed Kelly Ripa on live television. And he doesn't exactly have a sunny disposition to match the cheerful morning show. According to his IMDB bio, the last time Dave was on Regis' show was in 2004 when Kathie Lee was still co-hosting.

This morning, Regis Philbin announced to his co-host Kelly Ripa and his audience that he will be having triple heart bypass surgery later this week. He said he's been having chest pain and shortness of breath and "all those little symptoms you hear about". Reg, 75, would've preferred an angioplasty, he said, but there's too much plaque build-up in his arteries so major surgery is necessary. To lighten the mood, Kelly offered to be Regis' nurse and give him sponge baths.

It's not yet clear who is going to fill in for Regis, or for how long. It will probably be a rotating list of celebrity hosts. I can only hope that David Letterman will make an appearance or two- since Regis was so supportive and filled in for him when he had his quintuple bypass 7 years ago.