This scene pretty effectively creates the illusion of what it would be like to sneak up on some dude jacking off. Donatello spreads his porn magazine on the washer and gets down to business. He just pulls out his cock to jerk off, keeping his clothes on in case he's interrupted. The camera sneaks up behind Donatello just before he spills his Italian seed. He licks up some of his cum, before pulling himself together and heading out.
