Un-Cancelled: American Dad was cancelled in 2013 due to low ratings on FOX and inconsistent scheduling. However, TBS quickly picked the series up and renewed it for another season. Making it the second Seth MacFarlane show to be cancelled and saved from cancellaiton.
The Unfair Sex: The episode Stan Time is a perfect example of this trope. Throughout the episode Stan literally spends every waking hour waiting on his family hand and foot. All he asks for is time to read a book. When they refuse to give it to him he takes it in the form of pills that keeps its users awake, but well-rested. When Francine finds out about them she decided to take them as well. As mentioned Stan spends every waking moment waiting own his family. So when he doesn’t want to give up the time he set aside for himself Francine decides to keep taking the pills and eventually abandons Stan and her family. In the end it is Stan and no one else who has to learn not to take his loved ones for granted.
Punctuated by Francine having almost the exact same Aesop in a later episode, however while Francine learns to be appreciative of what she has, she is granted a fair compromise and some time to herself, something Stan is guilt tripped into thinking is hurtful and selfish in his case.
Much like Seth's other shows, this actually happens a whole lot, with Francine winning 99% of the arguments her and Stan have, regardless of the situation. Perhaps the most ludicrous case of this is in "The Kidney Stays In The Picture", where Francine is revealed to have had an affair just a day before their marriage. Stan is still the bad guy, to the point the affair is depicted as being for the best.
In "Bollocks To Stan", Hayley spends the whole episode switching between Bollock and Jeff, and dumping them in the most callous manner (as well as endangering Stan's career and the family's upbringing in the process). The Aesop is about Stan not treating her with enough respect.
The Unintelligible: Inverted with Toshi. He only speaks Japanese, but it's subtitled, so the audience can understand him but none of the characters can. This is lampshaded a few times, such as when Toshi mentions that he is haunted by the disembodied spirit of a 12th century samurai. When the spirit talks to him in Japanese, Toshi can't understand it properly.
He can also speak Russian and in one episode Francine ends a phone conversation with him with "Bueno gracias." Though the last may just be another joke about everyone perpetually misunderstanding him.
He actually speaks English at one point, after Snot yells at him to learn the language: "EAT... MY... BOWLS!"
Unreliable Narrator: Done in "The American Dad After-School Special". Throughout the episode, Stan is becoming ludicrously overweight despite all his exercise, apparently because his family is sabotaging him (injecting lard into his celery) to teach him a lesson about his hatred of fat people. Just before the commercial break, we see that Stan is in fact ludicrously underweight, having developed anorexia, his family was trying to keep him from starving himself to death, and his trainer, Zack, doesn't exist.
Francine is also capable of this, two prominent examples being when she screams at Stan for ruining her plan to break George Clooney's heart, and when after discovering that Stan tricked her into believing she committed murder, her response to him is angry to the point of psychotic.
More recent episodes have him sidetracked in his quest for boob, though - even to the point where he'll ignore it altogether.
Nobody seems to particularly care that Klaus and Reginald can talk.
In the fifth Christmas special, "Season's Beatings", Steve is possessed by the Anti-Christ early on, causing his eyes to turn red, his head to face the wrong way, and giving him the ability to climb on walls. The only reaction this gets from anyone is Francine telling him to "stop babbling at your sister in Aramaic. It's a dead language."
Very Special Episode: Subverted. Some episodes give the appearance of this before descending into chaos, as seen in Season Two's The American Dad After School Special, where Stan forbids Steve to date Debbie because she's overweight, then Stan realizes that he's fat too and becomes anorexic and "A Jones for a Smith" where Stan becomes a crack addict and eventually goes to rehab, but his son, Steve, is still pissed at him for ruining his chances with sleeping with a hot high school girl whose father was willing to let Steve be her first, and Hayley's pleas to be let into rehab for her marijuana smoking go unheeded.
Parodied (but played out very realistically) with "A.T.: The Abusive Terrestrial," which shows Roger's new friendship with a nine-year-old boy play out like someone being in an abusive romantic relationship.
Stan: I'm not a monster... (a human skull falls out of the furnace, which Stan quickly kicks back in)
One of the most extreme examples of this came from a Christmas Episode, where Stan accidentally killed himself, went to heaven, and found out that his family would die because of his actions. In the scenes that follow, Stan ends up fighting his way to confront God and holds him at gunpoint, demanding that he changes what is going to happen. God calls Stan out as a serious control freak, states that the very behavior that has brought him to this point is what has caused all of his problems and Stan isn't even slightly sorry for his obviously evil actions, and when Stan tries to argue, God says that Stan is holding a gun to God's head, demanding that he do as Stan wants. Even God can't come up with a better metaphor than that. Que Stan's My God, What Have I Done??
While Stan may have repetant or redeeming moments, Roger is as close to this trope as a sitcom character can get, and only gets worse with each season. A massive amount of humor is based around Roger's Lack of Empathy and life destroying (and occasionally life taking) schemes.
Vocal Evolution: Three characters come to mind when re-watching the pilot episode: Steve, Stan, and Klaus. All three had prominently deeper voices. Steve and Klaus's voices slowly increased in pitch, while Stan's became more refined in quality.
Roger's Paul Lynde basis was also more noticeable in early episodes.
Volleying Insults: We get this little exchange between Stan and Hayley in "Stannie Get Your Gun":
Hayley: You're such a fascist! Stan: Peacepusher! Hayley: Murder! Stan:Hermaphrodite!
A few moments later, when they continue exchanging:
Hayley: Gun toting maniac! Stan: Beatnik! Hayley: Warmonger! Stan: Chupacabra! Hayley: I'm the Mexican Bigfoot? Stan: You heard her, she admitted it!
VomitShots: One of the most recurring events in the series is for one of the characters (usually Stan or Roger) to vomit violently due to various reasons. It can be discreet, indiscreet, or outright over the top.
A couple people throwing up is all it takes to start a chain reaction of people throwing up in Mexico, where apparently they collect it and resell it as horchata.
Stan's relationship with his own father has elements of this as well.
What Happened to the Mouse?: In "Of Ice And Men", Svetlana, the Russian mail-order bride, marries Toshi after he steals her away from Snot. Nothing else happened to her. She's never seen again. This is lampshaded in a later episode when the topic of girls comes up and Toshi says "Didn't I used to have a wife?"
The Golden Turd Saga. Each time, someone would come across it and they become entranced by it, even doing drastic things to keep it. The last one featured the policeman's wife about to poison her husband when he suggested getting rid of it. The writers intended to show what happened next in a later episode but they weren't able to due to time constraints on episodes(and the writers admitted that they couldn't think of a satisfying way to continue the story). It's been several seasons since the last one, so the viewers are just left wondering what happened.
If one accepts that everything after the Apocalypse episode exists in Stan's Heaven then it was seen being used as the fuel for Roger's ship to get Stan and Jesus to the final battle with the Anti-Christ and to rescue Francine before Stan's death and gaining his heavenly reward.
What the Hell, Hero?: Everyone calls everyone else out on a pretty regular basis. Especially when it's one character's turn to be more heroic than usual.
Whole Plot Reference: Done very sparingly, and (usually) effectively; the show still manages to put its own unique twist on things even when it's largely basing its plot on an existing story. An excellent example is Irregarding Steve, which not only features Steve and Roger in a take-off on Midnight Cowboy, but has a running B-story which recreates What's Eating Gilbert Grape with squirrels.
The episode "Hot Water" is Little Shop of Horrors with a soul/R&B theme, Cee Lo Green, and a murderous hot tub.
Lampshaded in "Return of the Bling" when Roger bites Stan's finger off when the plot has already been resolved and they're literally ten seconds away from the credits, the only reason being "It was in the movie."
Besides the addition of a school election and revenge plot, the episode Escape From Pearl Bailey High is a near perfect homage to the cult 1979 movie The Warriors, complete with Principle Lewis taking place of the DJ informant.
Wham Line: "Now picture that boy [that was cut from the team by his dad] is you." -Steve
What Could Have Been: According to the commentaries, the original plan for Roger would've been that season 1 would've had him be stuck in the house all the time, but get fed up with it in season 2 and try the disguises. They would've worked until season 3, where Roger gets revealed in public and it becomes a giant media scandal. But by season 4, everyone would've gotten used to aliens and stopped caring, making Roger try to become the hot new story with schemes. Also, Klaus would've become a more mobile animal in Finances With Wolves, but didn't for some reason.
In ''1600 Candles" Klaus spends the episode in a hamster ball though. "Check me out! I'm MOBILE!!"
What Does She See in Him?: Played with for Stan and Francine. More evident in early episodes where Stan is more malevolent and chauvinistic, often leading Francine to suffer or be belittled in his antics (the smitten Klaus asked this multiple times and at one point was close to wooing her in a new human body). In later episodes however Stan becomes slightly more sympathetic while more emphasis is put on Francine's own unpleasant tendacies the former has to endure.
One early episode has this driving the main plot, with Francine's memories reverting to the state she was in during college, and Stan tries to win her back over, but she's put off by his being a "narc" as well as his violent attitude and rudeness.
[a voiceover of a lighthearted flashback plays as Stand pummels the elderly man] Lady: Dad, you're 76, just retire! Mark and I would love for you to live with us! Guard: Well, I can't leave the museum, Sheila, they need me! Lady: But these are your golden years! You should be enjoying life with your family! Guard: (laughs) I never stopped enjoying it Sheila... in a way, those paintings are my family...
Why Did It Have to Be Snakes?: Early in The Magnificicent Steven, Steve expresses an irrational fear of moths. Sure enough, later in the episode, he has to face a swarm of moths as part of the story. (Lampshaded by him saying, "Why did it have to be moths?")
Even better is Stan's bizarre, occasionally referenced aversion to seagulls. He even has nightmares about them ("Seagulls!? Francine - this time they could drive!")
Why Do You Keep Changing Jobs?: Officer Turlington, IRS/Spa Inspector/ Officer of Internal Affairs, who usually shows up to give the characters a really good, in-universe Mind Screw. As it turns out, he's just having a hell of a difficult time with his personal life as do the Smiths with their criminal activities, as demonstrated in "Meter Made", "Live and Let Fry", and "Chimdale".
Francine says this when Stan abandons her for Fussy the puppy.
Wig, Dress, Accent: Roger makes extensive use of these and could arguably fit into Paper-Thin Disguise territory from time to time. The show has even pointed it out by having him choose a disguise from an automatic rotating wardrobe full of outfits, and again in The One That Got Away when Roger changes into about a dozen of his characters in half a minute.
Wife Husbandry:Subverted, Steve and Snot rase two clone babies for prom to lose their virginity, but by the time Glitter (Steve clone daughter) and Honey (Snot clone daughter) are full grow, both Steve and Snot developed parental feelings for their clones and decide not to follow through on the sex, those that did not stop Snot from trying to have sex with Glitter.
A Wizard Did It: Roger has fooled Steve with these several times - once when Steve believed he was an actual Potter-esque wizard. Steve sometimes gets his revenge.
Women Are Wiser: For the most part. While Francine and Hayley are still incredibly flawed human beings, the male Smiths are usually depicted as far more dysfunctional and problematic, with the girls usually displaying more clarity and intelligence (or at the very least getting thrown An Aesop far less often). Most evident in "Rapture's Delight", while Stan's selfishness costs him his rapture, Francine is considered pure enough to become Jesus Christ's girlfriend.
Woobie, Destroyer of Worlds: Roger. He is so evil because his species releases a bile that kills them if they don't "let their evilness out". Made worse when it is revealed the reason he is trapped on Earth is that the others of his species wanted to get rid of him. In addition, there are moments where he really seems to care about his adoptive family. It is implied that Roger only acts that way because he was made to be evil, and not by choice.
Yandere: Hayley. If she's the one who breaks up with her boyfriend, no big thing. If she gets dumped, she will go berserk. It's gotten to a point where the police have issued Stan an ultimatum: If Hayley gets dumped and goes nuts one more time, she's going to prison.
Year Inside, Hour Outside: In The One That Got Away, Klaus is zapped into another dimension at one point. When he returns moments later, he claims to have been gone 60 years (and become the king of whatever place it was that he was visiting).
Roger: The second rule you can read on my website. You have to be 18 to log on. I have some sexy barnyard stuff on there that is not for everyone, I could get in a lot of trouble. If you do decide to check it out you're gonna have to clear your history right away- you may need to un-install your browser. I'm telling you, scrub that thing clean. If you think you're being too cautious you're not.They will take us both to jail.
Steve: Peanut Butter! Of course! That's my favorite thing in the world! If it weren't for the frozen moon of Saturn - Io, it would be my most favorite thing in the UNIVERSE!
Your Mom: In the episode Bully to Steve, Stan bullies Steve to make him tougher. He makes several Your Mom comments (worded as "Yeah, that's what your mom said last night!") towards him, which are likely true.