I think I liked these more when I assumed they were improvised. Scott Auckerman (Comedy Bang Bang, Mr Show) pretty much writes the material beforehand and the celebrities know what they're getting into. Or at least that was the case with the Obama one. That being said, all my stars for the awkward Friends theme song look.
Zoinks! Zach's 45 and Brad's 50! Personally I think Zach looks pretty great (I'm 32 and am starting to notice a few grey hairs in the old soup strainer) and he was really awesome in Birdman as a more serious actor.
Also bassoon jokes. As a bassoonist everyone in high school asked me if it was a bong and eventually I just went along with it. I feel kind of bad for doing this, but our school had a bassoon that nobody used except for me and I used it as a bong and it worked (better than our other options which were apples or 20 oz bottles of Josta Cola)