G.I. Blues - Multiple squatters can be found in the ruined store, being supplied food by the NCR's Supply Corps. They give generic dialogue when spoken to, and play no major role in the quest.
If the Courier decides to enter The Strip by going through Freeside, a squatter can be seen attempting to run past the securitons to enter The Strip, but he will be mowed down by the guards. This serves as a warning to not attempt trespassing.