Okay, here's the last batch of TV shows in which I think a flashback by the 'Lost' character of Charlie Pace could take place....
We wouldn't even need Dominic Monaghan for this one! Every Manhattan construction site has their plywood barriers plastered with old posters. So why not show a few tattered DriveShaft posters in the background of a crime scene?
What show could be better suited for flashbacks? Lilly Rush and her team could re-open a case in which a DriveShaft fan died during their Philadelphia concert. At the time, it looked accidental, or a drug overdose, but new information... information... information (Sorry about that, Chief!) leads the investigators to reclassify it as a homicide. DriveShaft would be seen performing on stage during the flashbacks.
Here's a chance at a triple play which could only happen in the imaginary world of Toobworld, Television Without Borders, because you'd never get three networks to agree on this merger!
The Montecito would be a great venue at which DriveShaft might have appeared and perhaps Danny saved some of the surveillance tape footage of them; something for him to use in comparison when a DriveShaft cover band shows up at the hotel. (Only to find out that the members of the group are the actual surviving members of the original DriveShaft, including Liam Pace! They could be appearing as "incredible simulations" of themselves in order to avoid the pressure of living up to their own legend.)
As for the 'CSI' half of this dream two-parter, maybe the forensics team could investigate the murder of one of those musicians in the DriveShaft cover band. That way Dominic Monaghan could actually appear as Charlie's lookalike, but not necessarily acting like him, and it wouldn't have to be in a flashback. (Unless of course he turned out to be the victim.)
'How I Met Your Mother'
'Lost' is a drama, but it has its flashbacks of humor. Although it would be fun to see Barney suit up to party with Charlie backstage, I'd rather see an old Robin Sparkles video in which Shablonsky got DriveShaft to be her backup band. (It might feel like a comedown for the band after its meteoric rise, but it would certainly be better than appearing in a diaper commercial!)
Another comedy. In this flashback, perhaps Johnny Drama took his younger brother Vincent Chase along to a backstage party for DriveShaft when they played Hollywood. And it could be that the "anything goes" lifestyle might have convinced Vince that this was the life for him.
Or Turtle could persuade E into putting "You All Everybody" into the "Medellin" soundtrack.....
One last suggestion, heading back overseas and across Time and the Relative Dimension of Space....
Here's a show in which Dominic Monaghan could appear as Charlie, without being stuck in a flashback. Instead, the TARDIS could appear at some point in his life and the Doctor and Martha could actually interact with the young musician before he got stranded on the Island.
Perhaps it could materialize during the Second Tour of Finland, and Charlie could be swept up in an adventure that involves a living legend from the Elder Eddas which is using the lyrics of "You All Everybody" to ignite Ragnarok.
Ragnarok 'n' Roll, baby!
Or maybe the Time Lord and his Companion made a re-fueling pit stop on the Cardiff Rift. That's where Charlie - in town for a concert and riding a heroin high - stumbles by, to take a leak against the TARDIS.......
So that's the lot; a chance for Charlie Pace to find even more crossover glory in the flashbacks of other TV series. I hope you enjoyed this dabblin' in wish-craft, you turnip-heads!