George is laying in bed with a red tube in his nose. A piece of tape to hold it appears and disappears between scenes.
Towards the end of the episode when 'purple' George is laying in the ambulance, he briefly lifts his head and there is a purple mark under his head on the pillow where the makeup rubbed off.
After George (Jason Alexander) calls Jerry (Jerry Seinfeld) a "jerk off", Seinfeld can be seen laughing.
When George thinks he's having a heart attack, an ambulance takes him to "Manhattan Memorial". The footage shows the ambulance speeding under elevated subway tracks. That El would be either in the Bronx or Brooklyn, certainly not on the east side of Manhattan, where the show takes place.
Kramer tells George Tor Eckman will heal his tonsils and adenoids, but Kramer was only told George needed his tonsils removed with no mention of his adenoids.