Sgt. Bob = Tom Brady, but not a douche like Tom Brady [ Updated ]
In a Trib article that may or may not include a quote from TPB Derek, there is tons of info regarding Sgt. Bob's rise to fame as the nation-anthem singer at CONSOL.  Jeff Jimerson was reached by the Trib at his secret lair for comment.

The switch prompted Jimerson to wryly cite Drew Bledsoe, the New England Patriots quarterback who got hurt and lost his job to a kid named Tom Brady.

"I can see the Penguins are embracing this," he said. "And I'm like, 'Uh, Jeff who?'

Now, the reason Jimerson missed Game One was because he was on a planned vacation.  He came back home in time for Game Two, and the Pens said no dice but only because of the insane phenomenon Sgt. Bob created. And because, according to a source, Bylsma and the players wanted him back.
Jimerson doesn't come off as pissed or anything in the piece. 
It's just a more general feeling of like, "What just happened here?"
Jimerson, Lange, and Barbero is a trifecta of vocal vitality.
Always will be. That's all we're saying.
But that said we're looking forward to Sgt. Bob's Game Five performance. The crowd is going to need a boost and Sgt. Bob will get things rocking..
Go Pens, Go Sgt. Bob, Go Jimmerson, GoAmerica.
And if you are going to the game stand up and sing. Oh man klmkldmkldm
Cblogger BabyPens99 nailed it:  Moral of the story: Never, never, never make any kind of plans (vacation, wedding, etc.) during playoffs.