I know my definition of pop is narrower than most people’s on this board, but pop isn’t even in the top 100 when thinking of words to describe this song.
I never heard that in the song.
Maxwell’s Silver Hammer is about as poppy as you can get, considering it’s about a serial killer.
Madonna’s “Live to Tell” is pretty somber, although it doesn’t seem to be referencing any particular trauma or event.
“Born in the USA” is about wasted lives, Vietnam, and the death of the American Dream.
Submitted for your consideration: Nick Lowe’s “Marie Provost” – a catchy little ditty that tells the more-or-less true story of Marie Prevost, “a winner/That became a doggie’s dinner”.
I’ll add “Bad Romance” to her list, as well. It’s about being in a relationship you know is a little fucked up, but decide to stay in anyway because eh, what the Hell.
“Brick” by Ben Folds Five, while not really upbeat, was still a pretty popular sing when it was released, is about the singer taking his girlfriend to get an abortion…based on a personal experience of the singer, no less.
That’s The Night That The Lights Went Out In Georgia-Vicki Lawrence
about committing and lying about murder.
Hmmm.
Maxwell’s Silver Hammer: A fine, upbeat little Beatles song about a sociopathic, murderous little shit.
Iron Man: Black Sabbath’s lovely tale of heroism, public ingratitude and apathy, and revenge.
Seasons in the Sun: Terry Jacks’ peppy adaptation of Le Moribond by Belgian singer-songwriter Jacques Brel. All about the last goodbyes of a soon-to-be-executed murderer. Saying farewell to the daughter who’s mother he killed, his father, and to the best friend whom seduced his wife, leading to the murder in the first place. Happiness!
I’m not sure if *Billy Don’t Be A Hero *could be considered dark, as I’m sure the intent was to tout Billy’s heroism, but you’ll not find a peppier song with more depressing lyrics.
You got your girlfriend crying in the first verse, a plaintive plea to not be an idiot in every chorus, a meat grinder for verse 2 and verse 3?
I heard his fiancee got a letter
That told how Billy died that day
The letter said that he was a hero
She should be proud he died that way
I heard she threw that letter away…
… followed by a jaunty little whistle. Who wouldn’t want to dance to that?
I am excited to be able to add arguably the sappiest song ever, “Seasons in the Sun” by Terry Jacks. (That counts as pop, right?)
ETA: I see that I spent far too long trying to figure out whether Cat Steven’s “Cat’s in the Cradle” also counted, and that as a result Tranquilis beat me to the punch.
I saw an interview with Third Eye Blind’s lead singer where he said that Semi-Charmed Life was supposed to be in some animated movie, maybe Shrek, but once the producers found out what was going on in the song, they pulled it.
According to Tranquilis, two posts before yours, yes.
ETA: But you can have credit for Cats in the Cradle.
Wikipedia actually calls “Cat’s in the Cradle” a “folk rock” song. I’m never quite sure about what counts as “pop”, so I passed on it.
Warren Zevon’s a master of this - I love Excitable Boy, a poppy, upbeat song about rape, murder and insanity (for extra marks, I’ll add that I heard it played at a real live junior prom in high school!)
For truly dark, an obscure old favourite from my nerdly youth - a pop song about the last guy alive on his planet, whose entire race was destroyed, and who now mans a lighthouse warning others to stay away … and then, he dies. 
Klaatu - So Said the Lighthouse Keeper:
[Part of a prog album that surely is a science-fiction classic]
The Wreck of the Edmund Fitzgerald
Dead Man’s Curve
Billy, Don’t Be A Hero
Pretty much the entirety of New Romantic/Goth influenced New Wave is “Dark Pop”, more because of the vaguely menacing, atmospheric, and/or depressing music than themes, although those can be dark, too.
Echo and the Bunnymen
OMD
Early Duran Duran
Some David Bowie
Arcadia
Plus at least 3 others that I don’t know enough to categorize. And doesn’t count the ones that fully abandon any rock pretense to become entirely synth such as New Order and Depeche Mode (as well as later dark synth pop bands such as Faith Assembly and Iris)
My favorite has to be “Santeria” by Sublime. Alternatingly peppy and mellow, it took me years to notice how gritty and violent the lyrics are.
Oh, I just thought of another one – "People Who Died" by Jim Carroll. Really makes you want to get up and dance!!
'S OK. We can loathe it together. 
In french, it probably makes a lot more sense - French is a great language for melancholy & irony. It doesn’t always translate well into English.
Ergh. Missed Edit window:
Oh, has anyone called out Maroon 5’s Wake Up Call yet…?
“…found you sleeping soundly
and your love is screaming loudly…”
Nice.
Can I nominate “Rikki Don’t Lose That Number” by Steely Dan? I don’t know if it’s so much ‘dark’ in the killing/cannibal/dying sense, but it does give off a tragically sad vibe. Depending on your interpretation. I don’t think some preggo woman (the writer of the song met her once and claims it is about her, her being the ‘Rikki’) is worth such a desperate, sad wail of longing and angst. I think it can be taken in another way, giving it real resonance.