Sam (Gregg's Character): ARC Trooper from an ARC batch designated Gamma, as it was the fourth batch created (after Null, Alpha, and Beta).

Granola: ARC Trooper from an ARC batch designated Gamma.  Squad-mate of Sam.  Good at tracking.

Ink: ARC Trooper from an ARC batch designated Gamma.  Squad-mate of Sam.  Has lots of tattoos.

Questions: ARC Trooper from an ARC batch designated Gamma.  Squad-mate of Sam.  Asks too many questions during briefings.

Jango Fett: Bounty hunter.  Template from which all the clones were created.  Trained Sam's squad, as well as most of the other ARC troopers.