28:04 – Behind the singing groupies there’s a sign that reads “No Right on Red.’ During the line “They say he saved her life,” a car can be seen turning on red.
28:30 – Penny is sitting in the Laundromat with TWO frozen yogurts, apparently expecting Billy to show. But he doesn’t, as he was too consumed with his plot to kill Captain Hammer.
33:33 – Penny can be seen with her arms crossed standing against the wall in the background while Dr. Horrible is singing.
35:05 – Dr. Horrible not only spills his own secret identity but we can see Penny behind some chairs mouthing “Billy Buddy,” making the connection that Billy is Dr. Horrible.
35:20 – After being punched by Captain Hammer, Dr. Horrible drops and bounces his death ray damaging it. Visible throughout the film and in the background was the Wonderflonium case for the death ray. On it, it warned “Do Not Bounce.”