Steve says his a capella group is called "Here Comes Treble". This is the name of the group that Andy Bernard was in at Cornell University on The Office.
The episode is based on films that take place during the Vietnam War such as Platoon, Apocalypse Now and Forrest Gump. The title comes from the film In Country with Bruce Willis.
The later parts of the episode are based on First Blood right down to Stan's army uniform and the final scenes.
When Stan is held captive by Roger for the code, his line "I'll make ya feel good" is based on a line from the film Boyz 'n the Hood.
Steve's performance at the end of the episode pays homage to Freddie Mercury (outfit) and Michael Jackson (singing).
Roger, dressed as a Vietnamese while torturing Stan, parodies The Three Stooges by waving his hand around Stan's face and then slapping him, then saying, in an Asian portrayal of Moe Howard's voice "A wise guy, eh?"
When Steve was in the hospital his roommate's name was John and they were in room 117. In the Halo series the main protagonist, Spartan 117's first name is John.
The Sex and the City draft Roger reads features Bugs Bunny's quote "What's up, Doc?"