Vicky bears a resemblance to Helen, a character from Zoomates, one of the cartoons that the creators, Butch Hartman and Seth MacFarlane both made.
Since Season 7 onwards, Vicky is the only remaining member left in her family to still make appearances in the series (despite her role getting smaller and smaller as time goes on), outlasting Tootie, Nicky, Her Dad, and Doidle.
In the pilot episode, she mentions having a little brother who can be heard giving a terrified scream over the phone. Apparently, if the brother does not do what Vicky wants, she says to her parents that he was looking at adult magazines. He has never been seen since, referenced or talked about in later episodes, and his only speaking role ever was a frightened shriek. Most likely this character was dropped and replaced with Tootie so that Timmy could have a love interest within Vicky's family. However he might have been either sent away for unknown reasons or was a lie made up by Vicky.
She did have a pet turtle at one time as a kid. However it died while she was at summer camp when she was 8 years old. She was lied to about the turtles death which is one reason why she is so mean all the time.
"Fairly OddPet" suggests that she might be taking out her frustrations on Timmy.
Vicky likes her pets and takes great care of them, unlike the children she babysits.
Recently revealed in "Frenemy Mine", Vicky was a part of a secret organization of evil babysitters (B.R.A.T.). Whether this is why she was mean to Timmy from the start or if she has her own hatred for Timmy is unknown.
It was revealed in "Boys in the Band" that Vicky apparently doesn't have any friends when trying to find a witness when planning her forced wedding to Chip Skylark. This was later enforced in Frenemy Mine, when she was kicked from the B.R.A.T. group.
In Wishology: The Exciting Middle Part, she cries out after Timmy is sucked into the Darkness, "I'll never call him a twerp again!". This reveals she has a love/hate relationship with Timmy.
Vicky enjoyed Poof's cute appearance in Wishology: The Final Ending. She even admitted she can't "resist the joy of a baby's smile."
From Season 3 and onward, Vicky's characterization has been exaggerated from being a mean bully to a sadist, including attempting to kill Timmy in many situations ("Vicky Gets Fired", "Open Wide and Say Aaagh!"). Most of the other evil characters in the show fear her and admit she is more mean than they are, in Certifiable Super Sitter a Season 10, she will so so crazy to the point where she breaks into timmy's house.
Vicky's hair color changed throughout the show from orange to red.
Her family's surname has never been revealed. Her house's mailbox just says "Vicky's House".
In Dream Goat!, Chompy the Goat was somehow able to give her a wedgie (one that was bad enough to make her go "Eep!") despite not having hands/fingers/thumbs--at the time, Vicky was shown wearing a pair of bright pink underwear.
She rarely ever calls Timmy by his first name (or even his last name). She typically calls him "Twerp."
While she is 16, it's unknown if Vicky has a driver's license, though she is occasionally shown driving.