Most quarterbacks approach the line of scrimmage and immediately locate the middle linebacker. The ‘Mike Linebacker’ usually dictates blocking schemes and sometimes whether or not a play needs to be change.
Cowobys quarterback Tony Romo identified Giants linebacker Jameel McClain as the ‘Mike’ on this play. McClain–doing his best Ray Lewis impersonation–returned the gamesmanship to Romo, and let him know he wasn’t the ‘Mike’ in hopes of confusing him.
h/t Snurf