His hair is the same style as Timmy Turner, except that it's colored green instead of brown.
Cosmo was originally designed as a fat bald lazy slob, a cross between Homer Simpson from The Simpsons and Fred Flintstone from The Flintstones. He was given a black tie to look like he was "always going to work" and to add to the show's 1950's feel.
He and Sparky are the only main characters to never wear Timmy's hat (Timmy wear the hat almost every episode, Poof in "Sooper Poof" (since he was adopted by Timmy's parents) and "Beach Blanket Bozos", and Wanda in "Tons of Timmys").
In the earliest shorts, Cosmo had a deep, suave voice, like a used-car salesman (described by Daran Norris, who also, in the documentary I Know That Voice likened the original voice to a bad imitation of comedian Phil Hartman), and was less moronic, and he and Wanda were both relatively careless and bubbleheaded ("We're two halves of a whole idiot!"). This has since changed, as over the course of the show Cosmo's changed from one half of a fairly goofy couple to the main source of carelessness and trouble, while Wanda's changed into a more sensible character.
Prior to the birth of Poof, he was the last fairy to be born, due to the destruction that he had caused as an infant.
Cosmo and Wanda are the only known Fairy Godparents to have two Godchildren at the same time, though it's implied that since there's a fairy shortage, there may be others as well.
Before he married Wanda, he was going to ask the Tooth Fairy for a hand in marriage.
He once bet Juandissimo Magnifico to Wanda for a nickel, which he apparently likes because of its luster. In another episode, he finds a nickel and names it Phillip. Phillip is a girl nickel (as noted in the quotes section below) and is seen in at least one other episode.
Cosmo, along with Wanda has been in all but one episode of the entire series.
There have been several instances where he has no brain, but somewhere he has a really tiny one, as shown in the first power hour. But his head is also full of grape jelly, a dancer was dancing on his brain one time, and sometimes, elevator music can be heard playing from his head.
He's got a pet hog named Steve that lives in his pants.
In the original cartoon, featured in 'Oh Yeah! Cartoons', Cosmo was actually smart.
Several instances (his name, in Timmy the Barbarian) refer to the name Julius.
His name in Greek means "world".
He supposedly wears a diaper. He has been seen wearing underwear most of the time, but after Fairly Odd Baby, he was seen wearing diapers throughout the show.
All of Cosmo's pets are named from Jimmy Neutron Characters (Carl the Ant, Cindy the Bee, Jimmy the Cat).
He often flirts with other female characters he deems attractive (e.g. Tooth Fairy) which often angers Wanda. He has also fallen for Princess Mandie, Blonda Fairywinkle, his reflection, a doll that was later transformed into Tootie, & various others.
He is the only fairy to go through an on-screen pregnancy.
He likes rice, pie, corn, lemonade, pudding and churros.
His favorite flower is the rose as revealed in the video game, "Shadow Showdown".
Cosmo's old band is called The Fairies. It consists of himself on the electric triangle, Eric Clapton on the guitar, Pan on the pan flute, Santa Claus on drums, and Ludwig van Beethoven on the organ (they were seen in Boys in the Band).
Cosmo is allergic to nuts, revealed in the "Squirrely Puffs" episode, although in past episodes he has been seen eating nuts without allergic reactions. The nuts he ate in Squirrely Puffs may have been a special kind of nuts that he is allergic to or that Cosmo takes a medication to prevent having an allergic reaction to nuts.
In the anime series, Sonic X, there is a character known as Cosmo in its third season. While both characters have the same name and color of hair, there are many differences, such as the fact that they have opposite genders and different eye colors.
He is apparently the reason why Denzel Crocker lost both him and Wanda due to allowing himself to be revealed to humans.
Cosmo's brain is probably located in butt according to Balance of Flour but other episodes strongly prove otherwise.
According to the episode, "The Gland Plan", Wanda stated that Cosmo was an only child but in the episode, "Double-Oh Schnozmo", his brother Schnozmo visits.
He was shown in the Big Time Rush episode, "Big Time Cartoon", and Budda Bob acted, talked, and being like Cosmo when he hit his head falling out of the ladder.
It is also revealed in Turning Into Turner that Cosmo doesn't weigh any pounds.
Cosmo is highly allergic to potato chips.
In A Sash and a Rash, it is revealed that Cosmo is allergic to peaches.
In This is Your Wish, it is shown that Cosmo lived with his mother before he married Wanda but in The Fairy Beginning he stated he lived with his Uncle Harry and Aunt Potter.
In most episodes his crown mysteriously is seen on the middle of his head this usually happens when he is next to Wanda.
Cosmo along with Timmy, Wanda, Mr. Turner, Mrs. Turner, Chester, AJ, Jorgen, Mark, Chet Ubetcha, Mr. Crocker and Vicky are the only characters to appear in every season of the show.
Cosmo, Wanda, Jorgen, Vicky and Mr. Crocker are the only characters to appear in every incarnation of the franchise.
"There's still enough pretty color left for one of us to slide down the magical rainbow bridge! Wow! There wasn't a single manly word in that sentence!"
[to Wanda] "Do you mind?! Your disembodied head is nag nag nagging next to my severed ear!"
"Ha! I'm licking the popcorn, so I don't have to share it!"
"I hated being a robot. I had no free will, I had to follow orders all the time, it was like being married all over again!! Except with more toast."
"So much clogging!!!"
"Either that or he wanted a banana."
"Or my favorite: WHEE!"
"I like monkeys!" (head flattens)
"Whoo Whoo Baby! Whoo Whoo!"
"Let's do the nag! You nag it to the left! You nag to the right! Come on everybody let's Nag tonight! I'm a living' doll!"
"Ah, the great outdoors, and no wife! Ooh yeah, I'm gonna swing, daddy-o! I'm gonna call on my old friends! (leafing through book) Let's see, Wanda, Wanda with a little star next to it, Panda, no that's Wanda with a smudge on the 'W'. I... I... (crying) I miss Wanda!"
"You always were great with dessert!"
"Well, she's not perfect, but she is the one who said yes."
"I slaved over a hot wand for this?
"I'm not bright, big words confuse me, I have the attention span of a rodent, and Wanda loves me anyway! She makes me happy, and that should be enough for you!"
Cosmo: If I could just light these candles, we could eat!
Wanda: Did it ever occur to you we're in a fishbowl filled with water?
Cosmo: That's why I'm trying to light these candles. Somebody's got to dry up all this wet food!
Wanda: We don't want to be her godparents! She's mean!
Cosmo: Yeah, we like Timmy better! His hat is pink!
"Yippie! That ouched!"
"Snowball!"
"A magic wand in the wrong hands could mean total disaster... and Vicky's hands are the worst hands around!"
"It's time for me to use the most powerful magical weapon in my arsenal: Me!"
Cosmo: Yeah! At least your parents aren't going away for the weekend and leaving your evil babysitter Vicky in charge!
Vicky: Surprise, twerp! Your parents are going away for the weekend and left me in charge!
Wanda: You gotta stop saying things like that!
Cosmo: It is my gift; it is my curse!
"Can we skip to Juliet's funeral?"
Timmy: This is a piece of cake. All I do is to find shapes, and I found them immediately!
Cosmo: And that is a piece of cake! Oh wait, it's just a barber.
"Word!"
"What?! What's the matter with you?! How could you say that?! I thought you loved me! What horrible future is this?!!!"
"What is this brain you speak of?"
"Well I'm a boob, and Wanda trapped me into marriage..."
Wanda: There are four basic elements: earth, air, fire, and--
Cosmo: JELLYBEANS!
Wanda: Don't we always have the best times?
Cosmo: I can't tell time!
"Good evening, everyone. We're your perfectly normal not-magic-fairy human waiters with unbelievably super-hairy legs and underarms!"
"String!!"
Wanda: Now Timmy, this is a lot more serious than one of your video games. We've lost our powers because of this Syndicate, and we won't be able to do anything until they're stopped.
Cosmo: Yeah, Timmy! Right now, this wand is just a glorified backscratcher!
