Do players try to outsmart or trick the refs sometimes?

Sometimes I see a receiver clearly not catch the ball, like it will skim off the ground before he scoops it up, and then he'll celebrate and do the first down signal, and act confounded when it's ruled incomplete. Or during a false start/offsides everyone on both sides starts pointing at everyone else on the other side to try to convince the ref that it was actually the other guy. Are they trying to manipulate the refs here or do they actually not know what happened themselves?