In "Kung Timmy", Cosmo says that Francis started puberty early.
According to an early pitch bible, Francis was originally going to be called Bruno Delvecchio.
Francis has the distinction of being the first antagonist in the main series after the Oh Yeah! Cartoons episodes.
Despite being since beginning of the canonical Fairly OddParents series, Francis is one of few villain characters who weren't make an appearance in the live-action movies, series Fairly Odder or animated reboot-sequel A New Wish.
He reveals he always wanted to be an interpretive dancer and is shown to practice.
Francis (along with Chester and A.J.) was originally going to be in The Bored Identity but was scrapped for unknown reasons.
Interestingly, despite the fact that he is a scary bully, in his last major appearance (Manic Mom-Day) he befriended Timmy (although it was Mrs. Turner in Timmy's body in reality). They danced together like ballerinas in the school bus. His true last appearance was in the episode "Dad Overboard" where Crocker dropped an F rock on him. This way, he could be considered a redeemed villain.
His father is the only member of his family to appear.
References
In "Hex Games", he is stated to be 12 years old by Vicky. Most likely due to low academic grades, Francis held back to 5-th grade, while he's supposed to be in 6-th or 7-th grade.
(About goldfish Cosmo and Wanda) "After I win 'em, I'm going to eat 'em, then kill 'em!
"Can we pick this up? I've got two beatings, three bludgeonings, and an intimidation this morning... and I don't want to be late for lunch. I'm having fish."
Francis: "Okay, Turner, can you guess what's behind my back?"
Timmy: "A hug?"
Francis: "Wrong! Wait, wha... a fist!"
Francis: [cleaning a litterbox] "I hate cleaning the litterbox. [You Doo magic forces him face-first into the box] Aah! There's nothing deodorizing about these crystals!"
[Timmy gives Francis a can of shave cream and a shaver] "Hey! This is gonna be fun!" [Goes to shave but gets cut with the shaver's razors and screams in pain] "Aaaaaah!"