There's no way to maintain a straight face at that, it's just not possible. Gus tries biting his lip, and then even has to move on to biting his own knuckle before Shawn is even done with his little speech. It's still all useless, because Gus starts laughing and can't stop until his gut hurts.

"If that was you trying to get me to go back to sleep, total fail." Gus grins.