How does Slim react to Lennie and George's traveling together?

Slim thinks the two men traveling together is a bit strange.....

Slim moved back slightly so the light was not on his face. "Funny how you an' him string along together." It was Slim's calm invitation to confidence.

"What's funny about it?" George demanded defensively.

"Oh, I dunno. Hardly none of the guys ever travel together. I hardly never seen two guys travel together. You know how the hands are, they just come in and get their bunk and work a month, and then they quit and go out alone. Never seem to give a damn about nobody. It jus' seems kinda funny a cuckoo like him and a smart little guy like you travelin' together."