Vegeta: They've broken my body... I've failed in my mission to get the Dragon Balls... I've even lost my tail... But at least, it can't get any worse from here... Ghost Nappa: Vegeeeetaaa... Vegeeeetaaa... Vegeta: W-What? Ghost Nappa:I'm haunting you! Vegeta:NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOooooooooo!
Krillin: We won't ever have to see him again! (Vegeta falls next to Krillin) Krillin: ... alive again. I meant we won't ever have to see him alive again! (naturally, Vegeta is alive)
In Episode 18, Vegeta brags to Goku that besides Freeza he's the most powerful being on the planet. Cue the Ginyu Force showing up.
"That's right. I'm your white mage. And nobody fucks with the white mage." Three guesses as to what happens immediately afterwards.
The frigate officer in the Warhammer 40K fan-film Damnatus — "We have never arrived too late before."
In Smashtasm there is a running gag wherein a character will say: "There's no way that ((insert bad thing)), especially not right now! Super64, being Genre Savvy, tries to invoke this trope when he gets captured, saying:
There's no way I could get out of here. Especially not right now."
The Lord of the Rings metafic epic The Official Fanfiction University of Middle-Earth tackles this in an early chapter, when the heroine spends a day with everything going wrong determinedly resisting the temptation to demand what else could go wrong ("for as everyone know, that is an invitation to get a demonstration of just what else can go wrong. The gods/God/evil forces/whatever you believed in were nothing if not equipped with a sense of irony. It's a vital God-quality, that."), until one thing too many does and she lets it slip. She then yells out that she didn't mean it... to no avail.
Tristan: I sure hope we don't encounter any more intrusive subplots. Jean Claude Magnum: Did somebody say "intrusive subplot"? Tristan: Oh, son of a bitch!
On the blimp:
Doctor: I'm glad I have such a long and villain-free life ahead of me. Melvin: Hi there. Could I get a hug? Dr. Feelgood: A hug? Sure, I don't see why not. (the sounds of chainsaw revving can be heard) Oh my god, it burns, it burns!
In the 26th video of Ultra J Man's Let's PlayI Wanna Be the Guy, he is still angry for a previous crash he had, and he declares "I get to the end, I beat The Guy, and it fucking crashes. That's how it's gonna end!"Guess what happens.
During the same video, Chuggaa points out how stupid it is that an NPC points out a very obvious hazard, wondering how anybody could ever get hit by them. He doesn't even manage to finish the question before he gets hit.
During the outtakes from the third Rival battle: "What the heck was I worried about, it's a freaking Rattata." Said Rattata then uses Quick Attack, gets a critical hit, and kills off his last Pokémon. "WHAT?! WHAT?! WHAT?!"
In Awesomeness Of The Ocarina this trope is inverted and discussed. "Even though Navi tempted fate with the dreaded "It can't get any worse" stock phrase, things actually got better. Link noticed this, but he didn't want to push his luck."
Subverted in episode 45 of Pretty Cure Heavy Metal. After taking a single whiff of a cigarette, Shugo says she doesn't want to get addicted. Guess what? She's remained smoke-free ever since.
Lampshaded in Harry Potter and the Methods of Rationality during the Stanford Prison Experiment arc. Dumbledore declared himself invincible and an Azkaban guard asks in astonished horror if he really just said that. Her commander says that he can get away with it since not even fate takes Dumbledore seriously anymore.
In A Hero, the second chapter has Dalek Sec watching Homura battle Walpurgisnacht from afar, and concluding that the Witch isn't looking his way, and wouldn't attack him. Fortunately, Sec's Genre Savvy enough to realize what he just did, which gives him just enough time to learn that a horde of familiars are heading his way.
This is referenced in The Man With No Name while some characters are infiltrating the enemy stronghold. It ultimately ends up subverted, however; despite the Doctor's expectations, nothing of the sort happens.
Inara: They seem to be expecting an auditor.
The Doctor: Good. No one will get too fussed when we go about asking nosy questions then.
Inara: As long as the real auditors don't show up, we should be alright.
In the Katawa Shoujo fic Lilly Epilogue Family Matters, Hisao narrates that "Considering that just one year ago I probably felt like the most pathetic sap on the planet, things are definitely looking up. Everything just feels right with the world." In the next scene, he finds out that his girlfriend Lilly's parents are coming to visit, prompting him to think "Ohfuck".
Mei: You know, this kind of creepy tunnel place with a load of dead bodies in it – well, dead robots, but it's the same sort of thing – you'd expect them to, like, get up and start attacking when someone poked one. Heidi: Will you shut up? You don't say stuff like that on a mission, do you want to make us all paranoid and jumpy?
In Perfection Is Overrated, after Midori tells the other Himes about what she's uncovered regarding the Hime Carnival, Shizuru tells her that there may not be much more time to find out, as one more incident with a SUE could force the school to shut down. Immediately afterward, Sekai the SUE unleashes an army of Orphans and Slave-users on the school, forcing them to evacuate the student body and fend off the invaders. Even though she's defeated, the school has to shut down, and Sekai is not even the last SUE they face.
In White Devil of the Moon, Fate repeatedly has to fend off Luna, Tuxedo Mask and the Outer Senshi, who mistakenly think she is a Dark Senshi who has kidnapped Nanoha (who is also Sailor Moon and the reincarnation of Princess Serenity). After the situation gets to the point where Fate has to tell Nanoha about it despite not wanting her to get involved out of Chronic Hero Syndrome and as a result, put a strain on her body, Nanoha remarks "At least we aren't likely to have any trouble show up at a wedding." At the wedding, Jadeite attacks in an attempt to kill Nanoha, who severely taxes her Linker Core by killing him with a Divine Buster.
The first line in Dashs New Mom, a fanfic where Dash struggles with her feelings over her father dating her same-aged best friend.
[Rainbow Dash's] life just couldn't get any better.
Her life proceeds to go sideways 15 minutes later.
Trunks' New Look ends with him saying this line, right before Goku, Chi-Chi and Gohan come in.
Trunks: How could things get any worse?
At one point in the Reading Rainbowverse, Fluttershy promised to pole-dance at Macintosh's wedding during a drunken rant. Once she sobered up, she immediately added the caveat that she "had to grow a horn first." Pinkie Pie, being very Genre Savvy, pointed out what she was doing, and Fluttershy pointed out that it was very unlikely for her ever to become an alicorn, and Pinkie would probably become an alicorn first...
As of this writing, Pinkie Pie is indeed an alicorn.
Picard: I'm sure there's nothing to fear in letting Admiral Thrawn examine our works of art.
When Shadowjack Watches Sailor Moon covers the first episode of Sailor Moon S, and a new monster is in the process of wrecking the entire team as they try to save Rei, Usagi celebrates when the monster complains:
Mikuji: "SO MANY DISTRACTIONS! JEEZ! What else could go wrong?!"
Usagi: "YES! She said it!"
ENTER Tuxedo Mask, dramatically, armed with +4 blessed throwing roses.
In A Stranger Among the Vopices, Twilight walks into the library after a stressful morning to be greeted by an explosion in the kitchen. "How can this day get any worse?" Rather hilariously lampshaded in the narration:
Seven words, seven innocuous words that when separated are as common as night and day. Many of the brightest minds had spent years researching the mystical power inherent when the words go together in the exact right order, and yet, none had ever come to a conclusion. It was even rumoured Clover the Clever had spent some of her years delving deep into their mystery but all to no avail. Twilight Sparkle, with all her past experiences really should have known better; at the end of the day she had no-one to blame but herself.