Two musical groups appeared as themselves; each one in a seperate dimension of the TV Universe.
First up, the Foo Fighters. Or as Josh Lyman found himself corrected, just Foo Fighters. They got a two-part appearance in the TV dimension in which Jed Bartlet is the President of the United States. They didn't play a significant role in the proceedings of 'The West Wing' except that they were the "house band" at the hotel where the Santos campaigners and party faithful were gathered for an anticipated victory celebration. Congressman Santos had to interrupt their set at one point to make the announcement that his running mate, Leo McGarry, had died of a massive coronary.
There must have been a collective sigh of relief among the production staff that they couldn't include Leo McGarry in the opening scene from the first episode of this season, which was set three years after Jed Bartlet left office. Had they done so, it would have been a give-away - one way or t'other as to how the election turned out. So when tragedy struck the show with the death of Leo's portrayer, John Spencer, last December, they didn't have to find a way to work around him to keep Leo alive.
So, knock on wood, nothing should happen to Dave Grohl and the other Foo Fighters before the election night of 2008. Not that it would mean it couldn't be splained away - sometimes characters in one TV dimension live longer than their counterparts in the alternate Toobworlds. We saw that happen often in the Mirror Universe episodes of 'Star Trek: Deep Space Nine'.
And it doesn't have to be anything as drastic as death. Who knows? By 2008, Foo Fighters may have disbanded in the Real World. But in that particular dimension, they'll still be performing together.
Come to think of it, let's hope nothing happens to Jon Bon Jovi before the 2008 campaign as well, since he was traveling with Santos in the final days of the campaign.
Over in the main Toobworld, Earth Prime-Time, the Dandy Warhols performed at the Trans-Alliance Center in Chicago "recently", as seen in the latest (perhaps last, but I hope not) episode of 'The Loop'. After the concert, Sam and Piper were invited to go to the party where they met lead singer Courtney Taylor-Taylor. Courtney immediately put the moves on a very vulnerable Piper (Her boyfriend had broken up with her... yet again.), much to Sam's consternation.
Luckily for Sam, Piper decided to go home rather than accept Courtney's invitation to join him in a "fourgy" (which she didn't know the meaning of. Duh!)
Courtney Tayler-Taylor has also appeared this season in an episode of 'Veronica Mars', where he sang at a local club's karaoke night in Neptune, California. Although he was addressed as "Courtney", it's not certain whether or not he was appearing as himself. It could be that he was just slumming on an off-night for the band, which is the way I'll be spinning it until a better splainin comes along....
After all, it makes for a televersion crossover between the two shows and I'm not about to pass one of those up!