- Adorkable: Billy is a total dork and Penny is almost messianically good, so when they finally start talking it's the epitome of awkward sweetness. Awkward because we know that Billy is a villain and that Penny probably wouldn't like that.
- Alternative Character Interpretation:
- There's a large camp of people who believe Dr. Horrible and Billy are two separate people in one body, as evidenced by some of the trope comments below, even though this was never revealed in the show.
- Also, whether it's a multiple personality or not, is Billy a genuine shy nice guy, or a passive-aggressive Nice Guy (TM) who, while less openly selfish in his pursuits of relationships than Captain Hammer, is not really any more interested in Penny as a person? It's a good story either way, but a very different story.
- Is Billy really in love with Penny, or just In Love with Love?
- Penny, on one hand, she dates a guy who's not very subtle about what a giant Jerkass he is because he's famous and can help her with her personal goals, she's possibly emotionally cheating on said Jerkass with Billy, and she quite possibly uses her last words just to twist the knife in someone's gut. The view of her as being full of Incorruptible Pure Pureness is more Billy's projection, and looking at what she actually does shows her as flawed and shallow like everyone else in the story.
- Then on the other hand, should she really be able to see Hammer's jerkiness? He's fairly low-key around her, until the press conference, where she sees it and doesn't like it a bit. Is she just using Hammer to achieve her own personal goal? Since her goal is a to help the homeless, is the manipulation unjustified?
- Are all the personalities of the characters due to Billy (the POV character) being an Unreliable Narrator? If you go by actions, Captain Hammer comes across as heroic Dogged Nice Guy while Billy is a villainous Stalker with a Crush. Penny meanwhile, hints at more depths with a Dark and Troubled Past than Incorruptible Pure Pureness she usually is. It's possible that Billy is justifying himself, demonizing Captain Hammer and putting Penny on a pedestal.
- There's at least one camp that argues that Captain Hammer is a much better boyfriend than Billy: neither of them are good, to be sure, but Captain Hammer at least gives her a level of respect and attention which Billy doesn't. This is largely derived from the fact that, when Penny suggests the homeless shelter to Billy, he dismisses the idea and says that she's not focusing on the real problems, suggesting a lack of interest in what Penny actually wants, and that Billy had been stalking her and his songs profess to giving her what he thinks she wants.
- Audience-Alienating Premise: Of the "good movie, terrible title" variety. Early on a lot of potential fans to watch it solely because the title "Sing-Along Blog" sounded bad. Fortunately, positive word of mouth eventually overcame the audience-alienating nature of the title.
- Awesome Music: Difficult to pick, as it's a chock-full-of-Moment of Awesome musical!
- Broken Base: One of the biggest cases in the fandom: is Penny's eventual fate a parody of the Disposable Woman, or is it just winking at the audience while indulging in it? Pretty much everyone agrees on there being an intent to parody, so the question is really whether Penny is actually characterized enough to defy her plot-designated status as a prop to be killed off for angst—some fans say yes, and others say no.
- Designated Villain: Weirdly, Captain Hammer ends up being this, despite being treated as an in-universe Designated Hero. He's a jerk, yes, but he actually listens to Penny, cares about her interests, and tries to do things for her, which Billy rather clearly doesn't do. He's pointedly mean to Billy, but Billy is... you know, a supervillain, who has rather evil motives even if he is Adorkable. He delivers a rather condescending song at the opening of a homeless shelter, but he's the one who opened the homeless shelter in the first place, and he does seem to be sincere in his understanding that it's a good thing to do, if nothing else. The bad that he does in the story is generally outweighed heavily by the good. His biggest failure as a hero is, oddly, probably that he's more interested in using excessive force against a villain he could easily restrain than in, ya know, actually arresting him.
- Draco in Leather Pants: The Fangirls/boys give this treatment to both Captain Hammer and Dr. Horrible.
- Ensemble Dark Horse:
- A literal case here with the Thoroughbred of Sin himself, Bad Horse; despite only featuring in two short songs and having a brief physical cameo at the end, just about everyone loves Bad Horse. He's a supervillain Godfather horse who delivers orders via cowboy-themed musical telegram, and has the amazing ability to sign phone calls.
- Despite only appearing in a contest entry video, Tur-Mohel quickly became a standout, as did Mr. Terrible for his Villain Song.
- Fandom-Specific Plot: Many fanfics in the fandom tend to fall into one of two categories: One where Penny never dies at all, and another where she dies but Dr. Horrible uses his new resources to bring her back to life, with varying levels of success.
- Fashion-Victim Villain: Apparently, silly costumes are a requirement for the Evil League of Evil.
- Faux Symbolism: Dr. Horrible's overlarge armchair in which he plots world domination. Either he feels inadequate or it's just for comedic effect. See the Jossed entry in Trivia — that chair just happened to be in the house where they were filming.
- Foe Yay: Between Captain Hammer and Dr. Horrible, who seem to take their relationship very seriously:
- Dr. Horrible mentions at the very beginning of his blog that Captain Hammer is his nemesis, not some poser in a parka. Captain Hammer apparently returns the feeling as he admits in his song that everyone's villains aren't as cool as his.
- "These... Are not the hammer. The hammer is my penis." One act later, Dr. Horrible taunts him with "Hammer, meet nail!" If that's not a Metaphorgotten, it's a very revealing Freudian Slip.
- "Funny Aneurysm" Moment: One of the Evil League of Evil leaders being named "Dead Bowie", yeah.
- Harsher in Hindsight:
- The fan reaction to Loki in Whedon's film of The Avengers is eerily similar to how the public react to Dr. Horrible in the ending, especially considering that they had the same motives (taking over the world in an effort to make it a better place) — Loki kills hundreds of people, but he's still worshipped as a villain, just like Dr. Horrible was, complete with obsessed fangirls.
- As noted in this video by Sarah Z, Billy/Dr. Horrible's character arc can easily be interpreted in hindsight as metaphorical for the radicalization of young men into various anti-feminist/toxic masculinist ideologies, particularly the incel movement, at a time when they were barely a blip on the cultural radar. Billy starts out as a dweebish, nerdy man who pines after Penny, yet she winds up instead attracted to Captain Hammer, a paragon of traditional masculinity who earns Billy's resentment for it — not unlike many self-proclaimed incels who blame "Chads", their generalized term for men (particularly handsome, athletic, and successful men, the term meant to evoke high school Jerk Jocks) who are more successful with women than they are, for their perpetual datelessness. His journey to win Penny's affection winds up getting her killed, the moment at which his slide into supervillainy and transformation into Dr. Horrible is complete, reflective of various self-proclaimed incels who have gone on killing sprees.
- Hilarious in Hindsight:
- The line "Let's all be our best" from "So They Say" is now quite reminiscent of another Whedon work.
- In this short, Felicia Day is the love interest of a supervillain. A few years later she became a supervillain herself.
- Simon Helberg plays the friend of a nerdy scientist with a love interest named Penny.
- Hype Backlash: There are some that feel that the short — which is low-budget and only 45 minutes long — doesn't really live up to the massive praise heaped upon it by its fans.
- Iron Woobie: Dr. Horrible has taken a ridiculous amount of abuse, and he doesn't remotely look like it. Hammer threw a car at his friggin' head!
- Jerkass Woobie: But at the same time, Dr. Horrible is a Card-Carrying Villain.
- Memetic Mutation:
- "The Hammer is my penis."
- "Shiny New Australia".
- Misaimed Fandom:
- Some people, as highlighted in this essay, are arguing that a large part of the audience seems to have missed the point especially in the way it tackled the idea of Disposable Woman and of Billy as a Nice Guy. Billy's complete transformation into the Dr. Horrible persona is clearly and unambiguously portrayed as a tragedy; not only because of the loss of Penny, but because it costs him the very humanity that his friend associates with. Some people are still going to prefer the Well-Intentioned Extremist Dr. Horrible over the nebbish Stalker with a Crush Billy.
- Some YouTube comments imply that a few people wish they could deal with their bullies the way that Billy goes on to do. This is slightly worrying, to say the least.
- Moral Event Horizon:
- Captain Hammer dating and sleeping with Penny just because he knows it'll hurt Billy/Dr. Horrible. He might be a superhero, but this moment makes it clear he's not in it because he's a good person. This is ultimately what causes Billy to plot to kill him — not the countless times Hammer's foiled his crimes and beaten him up.
- While Horrible views it as... horrible, having sex with a fellow consenting adult and your girlfriend isn't really bad by any reasonable moral standard, even if Hammer is a jerk. Hammer's real MEH moment came near the end, when he outright tried to execute a downed and defenseless Dr. Horrible with his own death ray while the latter was begging for mercy. Supervillain or no, that's outright murder by any legal definition. He's only prevented from doing so by the death ray's malfunction... but that just means he (accidentally) kills Penny instead.
- The fact that Bad Horse orchestrated the events that led to Billy and Penny's fate.
- Nightmare Fuel: The comic Best Friends Forever has Billy, needing to wake up from a dream, demand a vision of Penny ask why he killed her while gorily melting into a skeleton, with no in-between panel to soften it. It's implied this has happened many times before, as Penny doesn't like it but it's the only way to wake him for sure.
- What an Idiot!: Captain Hammer managed to damage the device which allows Dr. Horrible to control the truck with Wonderflonium.
You'd Expect: That Captain Hammer would stop the truck immediately.
Instead: He jumps off the truck to flirt with a woman on the street. The truck goes out of control which could have injured or killed someone which nearly happened to Penny. On top of that Horrible managed to steal the Wonderflonium.
To be fair: He at least tried to save Penny by pushing her into the trash, but there is no denying that his actions were very reckless.
- What Do You Mean, It's Not for Kids?: A lot of parents seem to think that because it is a musical, the show is perfectly fine for small children. Considering that it's centered around a villain's Start of Darkness and it sports lyrics such as "It's a brand new day, and the sun is high / All the birds are singing that you're gonna die"...yeah. A lot of it probably goes over the kiddies' heads anyway (one would hope), but still...
- Felicia Day mentions, in one of the commentaries, a fan who wrote to tell her "my nine-year-old daughter loved you in this...until Act 3."
- The Woobie: Not only does Dr. Horrible get roughed up on a regular basis but takes it in stride ("... honestly, I'll live."), he suffers the emotional equivalent of a punch to the gut several times. "Penny's Song" establishes Penny as this to some extent, although she's far too optimistic to let it stick.
YMMV / Dr. Horrible's Sing-Along Blog