Timmy's wish for Christmas Every Day is what caused the problem in the first place. Timmy's wish was so bad, they had to make a new rule. The rule was that no child could never ever wish for Christmas every day.
Screens Are Cameras: In Information Stupor Highway, Crocker uses a spyware program to see what's happening in Timmy Turner's room. How does the program do it? By filming the room through the monitor of Timmy's computer.
Second Person Attack: Used several times: at least two in Abracatastrophe; one in the beginning of Channel Chasers; in the episodes "Mighty Mom and Dyno Dad", "Scary Godparents", "Kung Timmy" (and several others), and occasionally in the Crimson Chin bridging sequences in the Season 0 episodes.
Secret Identity: Charles Hampton Indigo for the Crimson Chin; Timmy himself for Cleft the Boy Chin Wonder
Selfless Wish: Timmy needed money to buy tickets to "Crash Nebula: On Ice". He can't simply use his fairy godparents to wish for the tickets because it'd be theft and he can't wish for the Money so he opened a Lemonade Stand but his lemonade had a horrible taste until Cosmo dipped his used socks on it, which also caused the lemonade to grant wishes to anyone who drank it. After using almost all his lemonade to undo the damage caused by his customers, he intended to use the remaining lemonade to get the tickets but then he saw a thirsty boy who was forced to work making lemonade for Vicky's stand and Timmy decided to give him the lemonade and the boy, unaware that the lemonade would grant him a wish, wished for his Dad. The kid's Doug Dimmadome's long-lost son Dale Dimmadome. Doug Dimmadome owns the place where the show's performance would take place and rewarded Timmy and his friends by giving them Jobs selling lemonade at the stadium. (Giving tickes was not an option because all tickets had already been sold)
Otherwise, Timmy's selfless wishes don't count for the trope since his wishes are not limited by number.
In "Fairy Idol", Chester used his last wish to undo the damages caused by Norm.
If one counts Grow Up, Timmy Turner as canon, he's no longer allowed to make anything but selfless wishes.
Shipper on Deck: Cosmo and Wanda apparently like it when Tootie kisses Timmy, even though they are obligated to use their magic to help Timmy avoid her.
Short Run In Peru: Started with the two episodes Timmy the Barbarian and No Substitute for Crazy, two episodes of the fifth season, being shown in the UK first. However, Nickelodeon now seems to show several first run episodes of FOP first in the UK and Latin America, and then weeks, sometimes months afterwards in the United States. A prime example of American audiences being Screwed by the Network.
This also happened to Butch Hartman's other show Danny Phantom during DP's final season. Apparently Nick likes to screw with Hartman's American fans.
Shown Their Work: The "Maho Mushi" segment at the end of Channel Chasers is anything but a Shallow Parody. Doubtless that segment was included due to the Dragon Ball Z craze, but it doesn't parody Z at all - it recreates the Piccolo Jr. arc at the end of the relatively obscure original Dragon Ball. Note Vicky's attire and the fact that the battle takes place in a tournament ring.
Side Effects Include...: When Jorgen was about to erase Timmy's memories of having Fairy Godparents during the second part of "Fairy Idol", he said he'd use more "forgeticin". Then the viewers got an ad about forgeticin. The announcer forgot who he was and what he was doing while announcing side effects.
Sparse List Of Rules: Fairy Godparents are restricted to a large list of rules listed in a gigantic book titles 'Da Rules'. Cosmo and Wanda would pull out the rule book any time Timmy plans on making a wish that would break the rules. It's never said how many rules there are, but new ones are mentioned frequently.
Spell My Name with an S: There's confusion over wether it's Juandissimo or Wandissimo. Production art spells is as the former.
Spotlight-Stealing Squad: Since season seven onward, Denzel Crocker, Timmy's dad, Poof and Foop have more and more amount of screen-time in the show. Sparky in Season Nine.
Squashed Flat: The show sometimes employs this trope. One prime example is when Timmy's parents charge him with guarding his parents case of glass figurines. The Greek Gods of Mt. Olympus show up. One of them is about to strike the glass case, Timmy steps in front to prevent it's falling and it falls on him. When the case is removed there is a very, very flat Timmy on the floor.
Stalker Shrine: Tootie's entire room is one of these with shrines, pictures, dolls of Timmy. Veronica has something similar...with Trixie. Timmy sometimes has one of these in his bedroom for Trixie Tang as well.
Stalker with a Crush: Timmy has three: Tootie, Veronica, and The Darkness. And Juandissimo to Wanda.
Even a monkey wanted to do it in Abra-Catastophe, if Cosmo's monkey language abilities are to be trusted. Well, not so much take over the world as have apes take over the world, and have him take Timmy's place. Or a banana.
Take That: In When Losers Attack, Crocker, Foop and Dark Laser end up getting sucked into a black hole and fall into a random cityscape.
Crocker: Hmm, I wonder where you end up after going through a black hole. *town sign reads "Welcome to Bakersfield"* Einstein was right!
"Timmy's 2-D House Of Horrors" takes unyielding and relentless bashings towards the 3-D movie phenomenon.
School's Out: The Musical revealed Flappy Bob's parents checked every clown-congregation spot in the county. And then Flappy's dad adds: "we even checked the U.S. Congress! It was full of clowns...but none of them were fun!"
Chindred Spirits in an interesting example. On the surface, it looks like a Take That at comic book Fan Dumb who are overdosed on action and dont' care about characterization, except the Chin's comic is being boring due to his want of romance/dating Golden Locks (oddly making Timmy in the right, even though it acts like he's not). So it's really a Take That at overly Wangst- or fluff-laden romance-arcs in comics.
"Dadbra-Cadabra" has a quick one, a sign reads "Hoboken, population 39,900 hoboes"
"Farm Pit" has one towards Cleveland, their sign is "Welcome To Cleveland, now go home!" and the city is also shown to be full of crime scenes.
"This is Your Wish" has Cosmo destroying or ruining three ancient or mythical cities, the third being Xanadu turned into a polluted, smog-infested city full of factories.
Cosmo: I call it Pittsburgh!
Take That Me: "Everyone knows that comedy is the lowest form of entertainment! Except animation."
Talking to Himself: Timmy, Poof, and Princess Mandie; Cosmo, Mr. Turner, Jorgen, Anti-Cosmo, and The April Fool; Wanda, Mrs. Turner, Blonda #1, and Anti-Wanda; Vicky and Tootie; The Mayor and Chompy the Goat; Sanjay and Elmer; Mark Chang and King Grippulon; Crocker and Juandissimo in "Teacher's Pet".
Taught by Television: A literal example is Poof in Wishology, but TV is treated as the solution on multiple occasions.
Those Two Guys: Chester and AJ started out as Timmy's two best friends, but ultimately became more associated with each other - sometimes even separately from Timmy. Cupid and Juandissimo sometimes as well.
Tomboy and Girly Girl: Vicky and Tootie. This is shown in contrast especially in the episode Timmy's 2-D House of Horror where the two sisters took over Timmy's bedroom; turning one half into a pink and girly room with unicorns, and the other half into a medieval dungeon.
Seen with Trixie and Veronica. Trixie is secretly a comic fangirl while Veronica is a cheerleader Valley Girl stereotype.
Torches and Pitchforks: Mother Nature and The Secret Origin of Denzel Crocker, where the torches and pitchfork crowd is still chasing him decades afterwards.
Happened again in another episode where Poof uses his magic to switch Timmy's head with a nearby housefly so they could sneak out and watch a movie. When his dad discovers the fly-headed boy, he rouses up an angry crowd of medieval looking townspeople who try to end the creature while wielding torches and pitchforks. After Timmy undoes the wish, his Mom reminds Dad not to do it again, suggesting this has happened many times before.
Trailer Park Tornado Magnet: There was one episode where Timmy meets Cosmo and Wanda's previous and infamous godchildren. One of them proudly takes credit for wishing that tornados always hit trailer parks.
Tranquillizer Dart: An episode in which a Drill Sergeant Nasty, Jorgen von Strangle, is quickly rendered insensate using two darts (humorously marked "K" & "O") during a fit of animalistic rage.
Trash of the Titans: When Timmy accidentally wrecks Mount Olympus for partying with the gods too hard, they decide to all party as his house until such a time that Wanda has Olympus rebuilt. He does everything in his power to prevent them from destroying everything.
Tsundere: Wanda. Vicky might also be this; while usually violent, cruel, cold-hearted and sadistic, she seems to melt like butter for the guys she falls in love with. And for some fans, hinted in Trixie Tang.
TV Telephone Etiquette: Timmy talks in a three-way split screen with his friends Chester and AJ. After the conversation, Timmy and Chester hang up without saying "Goodbye" Poor A.J. was left on the line.
Twitchy Eye: Trixie when she goes insane in Just the Two of Us
And Timmy when his mom shows him that her old swimsuit still fits.
Unknown Rival: The Dinklebergs to the Turners. Subverted in Operation: Dinkleburg. Dinkleburg has known of Mr. Turner's one sided rivalry for years and truly holds no ill will in turn. He plays the villain when Mr. Turner accuses Dinkleburg of being evil just to give him the satisfaction of believing he was right.
Useless Spleen: In an attempt to beat Timmy up while Timmy blocks his attempts with his newly-gotten attendance award, Francis can be heard shouting "Ow, my hand! Ow, my other hand! Ow, my head! Ow, my spleen!" as he continues to take swings.
Villainous Crossdresser: Timmy managed to humiliate Crocker on a global scale and get him arrested for developing a supposed computer virus by uploading a video file of himself modeling one of his mother's dresses.
"Oh well, I suppose it does make me look pretty."
Villain Song: "Pixie Rap", "Gimmie the Wand", Vicky gets a few in the comic story The Babysitter Sings
Vocal Evolution: Probably as a result of the increasingly updated sound adjustment and the advancement of the actors' voices, almost every one of the show's characters went through this at some time or another.
Cosmo sounded more like a game show host in the Oh Yeah! Cartoons pilots and first two seasons.
Crocker's voice was much softer and toned down in his first few appearances, although it had to change to adjust to his growing insanity over the advancing seasons.
Chester and A.J. sounded exactly like their estimated ages in the first couple of seasons, before their voice actors were replaced and they sounded much older as a result.
A Weighty Aesop: The episode "Just Desserts!" in which Timmy wishes that it was dessert all the time. By day 28 of the wish everyone is severely obese and gets to the point of rolling around. The extra weight causes the Earth to tilt on its axis and spin towards the sun.
What Could Have Been: Originally Timmy was going to be a redhead because Butch Hartman hates brown hair, but forced to change his mind because he didn't want Timmy and Vicky to have matching hair color. Also Timmy was almost named Matt after Butch's other brother, but an argument with his brothers changed that. Timmy's shirt and hat were meant to be blue, but Hartman ran out of blue marker and grabbed the next nearest color—which just so happened to be pink. It stuck.
When I Was Your Age: Timmy's paternal grandfather is quite fond of the trope. His first non-flashback line was a rant about how he doesn't like things as how they're today when compared to what they used to be.
Where the Hell Is Springfield?: The show takes place in fictional Dimmsdale. It turns out there IS a place called Dimsdale. It's in northern Canada. The series later revealed the town is in California, but only on the map, and not by name.
The episode "Meet the Oddparents" narrowed down the location. At the end of the episode Jorgen invokes his authority from Whittier, California while erasing Timmy's parents memories. Whittier is a city south-east of Los Angeles. Its not much of a stretch to think that Dimmsdale lies in the same general area.
Your Size May Vary: Timmy is shown to change in size from scene to scene. In the early seasons before Mom and Dad were given faces, Timmy was small enough to sit completely in Dad's hand.
Fridge Brilliance: Timmy would reasonably have grown and his perception of his parents as giants vanished. Also his size in later episodes (at least those without shrinking) is more-consistent.
Zee Rust: For the episode Future Lost. Timmy finds an old comic book that decribes the "far off" future of the year 2000. He notes that the real 21st century is nothing at all like what's in the comic book.