In the part where Duke is talking to Samantha while they autopsy the dead imp, Duke asks about what John was like before he enlisted. Here is the conversation:

SAMANTHA: Who, John?

DUKE: Yeah.

S: Empathetic, Sensitive.

D: It's kinda hard for me to imagine Reaper as sensitive.

S: Well I knew Reaper before all the drop-down-give-me-fifty wooha stuff.

D: Yeah? Well it's Hooah.

That's the slip up part. The RRTS are supposed to be Marines, but its the Army that says "hooah". The Marines say "oorah" not "hooah".