The character of Mr. Crocker, who desperately tries to uncover Timmy’s fairies in the series, was inspired by Walter Kornbluth, Eugene Levy’s character from the 1984 feature film Splash, who tried to prove the existence of mermaids.
According to Fairly Odd Christmas, Crocker doesn't really needs glasses; he uses them to look smart/like a geek. Also, it was revealed that Crocker dyes his hair and he's actually a redhead.
In the video game Nicktoons Unite during the battle with Crocker, he was wearing a gold armor but in the final battle with the other villains, Crocker was in his teacher clothes.
His voice sounds similar to Mr. Burns, a character from the animated series, The Simpsons, which Butch Hartman is fan of that show. Also, both characters have a hump on their backs and sometimes Crocker says "Excellent!" like Mr. Burns.
Butch Hartman originally created Crocker for another show of his that did not get made. After plans for said other show were canned, Crocker was integrated into the Fairly OddParents cast. Also, according to Butch Hartman's list of favorite episodes on iTunes, Crocker was originally intended to be a one shot character.
Until recently, his overwhelming belief in fairies was the sole source of power for all of Fairy World. Since the end of Crocker Shocker, people similar to him are also used as the sources of power for Fairy World.
In "Pipe Down", Crocker spots Timmy, Cosmo, and Wanda and does his usual fairy godparents spasm frantically, but since there is no sound, no one, for once, can hear him scream!
Denzel Crocker has made more appearances since Season 7 onward, replacing Vicky as the more frequent adversary of Timmy in the series. His appearances exploded in Season 9, appearing in almost every episode. Though many of these appearances were minor, and their usual purposes were punch line jokes.
Possibly the reason why he gives so many F's to Timmy is probably because F is the first letter in the word fairy, but also the fact that he believes that Timmy has Fairy Godparents which he does, but the first reason is not confirmed.
He is one of the few, if not the only character with a theme song that plays in the title screen of any episode he is the antagonist (or, similar arranges). Curiously, it's the same arrange in Abra-Catastrophe!'s opening, a movie where he is the main antagonist.
He's been hunting fairies since 1975.
He's at his worst at March 15th.
Mr Crocker is very similar to Mr. Lancer from Danny Phantom. They're both weird teachers whose dialog features frequent sarcastic humor, they're both treated with disrespect, they're both under-paid and under-appreciated, and they're both creations belonging to Butch Hartman.
Saying "Fairy GodParents!" "Fairies!" "Fairy!"
Giving Timmy "F's" in every class.
Saying "This may be the work of..." (In Birthday Wish!, he said the same thing to Tootie, but in one scene he said "Is this cake may be the work of...give me a second...[Inhales] Fairy GodParents?!" when Tootie has Timmy's fairies because of his guiltiness of Timmy not seeing 3 invitations and just looked at the coupon)
It's noted in "Formula for Disaster", that Crocker once was in Ninja school, was taught to be a ballerina, wanted to be a cat burglar (but didn't know what to do with a bunch of cats, a pun on the term for a jewel thief), and could never (ever, EVER) go back to Cincinnati . As a matter of fact, a sign at the end of the implied episode has "CROCKER FREE SINCE '83" at the bottom, with two Anti-Crocker stickers at the bottom, below the saying. It seems he was banned from Cincinnati in 1983.
In Remy Rides Again, Crocker states that Stephen Hawking was his college roommate, which indicates that Crocker must have been born around 1942, because Hawking was born that year. This is impossible since he was seen as clearly being 10 years old in 1972. This means that Hawking was born in 1962 instead of 1942 in the Fairly OddParents universe since there is often anachorisms in the show relating to people's ages (Adam West is shown younger in this universe even though he should be around 80 at this point).
Despite Crocker being born in 1949, he is 10 years old in 1972, when he should really be 23 years old. This is likely because of storyboard artists that are different, and probably don't know about the previous storyboards.