The rumor that Sarah Michelle Gellar had a cameo in the third act of Dr. Horrible was later confirmed in the DVD commentary. She is sitting in the audience next to the goupies, wearing pink-rimmed sunglasses, a pink scarf, and a black wig. This wig resembles the one that Gellar wore in the episode Restless of Joss Whedon's show Buffy the Vampire Slayer.
The newspaper article under the headline Girlfriend of Captain Hammer Murdered reads:
"Our Hero Captain Hammer had a girlfriend, but now she is dead. She was murdered in an unprecedented event that took place down at a new homeless shelter. The event was for the opening of the new Caring Hands Homeless Shelter and it was going to be a great big party till Dr. Horrible messed it all up."
These three sentences are then repeated.
The newspaper headlines after Penny's death read:
"Heroes Girlfriend Murdered; Girlfriend of Captain Hammer Murdered"
"Country Mourns Whats-Her-Name"
"Worst Villain Ever; Dr. Horrible"
In the beginning of the Act, the NBN News headline at the bottom of the tv screen reads:
Captain Hammer: "I hope to set an example, you know, for children and stuff."
In the end, there is another NBN headline, shown while newswoman and newsman are crying:
Tragedy: Dr. Horrible Defeats Captain Hammer. Hero "Unavailable for Comment" for First Time Ever.
Camouflage: In this installment, Dr. Horrible is revealed to be a master of disguise, appearing both as an ambulatory bush and a mustachioed soup kitchen attendant to sneak up on his nemesis, Captain Hammer.
There has been much speculation by fans that the pots and pans hanging behind Dr. Horrible during his videoblog are a reference to the kitchen area of Serenity, the space ship featured in a Joss Whedon movie of the same name (Serenity) and his series Firefly that precedes the movie. According to the blog of the actual owner of the house where Dr. Horrible's lair is set, this is not an intentional reference but simply where he hangs his cookware.
The remote control used by Dr. Horrible to steal the courier van appears to be an Apple iPhone. The phone service provider, AT&T, is listed in the top-left corner of the phone.
Dr. Horrible's Weaponry:
He has created a device that will home-in on a vehicle, attach itself to the roof, and then allow the user to control the car remotely.
He claims that his transmatter beam is functioning at about 75 percent, although it apparently turned gold bullion into a substance that is liquid at room temperature and smells like cumin.
He is also working to perfect a ray that stops time. The demonstration he envisions during the song My Freeze Ray seems to suggest a very localized freezing of time, relatively speaking. Its precise function is unknown but it is not an ice beam.
In the final sequence of A Man's Gotta Do, he secures possession of wonderflonium, the final component he requires for the Freeze Ray. Little is known about wonderflonium but it shouldn't be bounced.
Also, there are various unnamed inventions visible in the background while Dr. Horrible is recording his video blog.
Sitcoms, love triangle, mad scientists, musical numbers, quirky soundtrack