Denise used to be an AIT back in the 1400's until she used a body swap spell on a raccoon puppet and became trapped in the body of Dennis, the previously mentioned raccoon puppet. Not skilled enough to redo the magic she became stuck and slowly began to sound and pick up the mannerisms of a raccoon and went by the name Dennis for many years. She was in the puppet so long that she began forgetting who she was which prompted Dr. Cassabi to remind him once a year.
Theres one upside about Denise being trapped in the raccoon puppet. She complained about having to do her A.I.T training in the stupid ages with the humans not having advanced real far. Now in the 21th century humankind has advanced much further. So in the end she got what she wanted. (Too bad it costed her roughly 400 year of her life but then again she is immortal so years shouldn't really matter to her). She almost got a new A.I.T assignment in the episode me Carl You Janish but just when she was about to receive it Porter beamed to her location with the zombie Jane duplicate she had created causing the A.I.T Revision Council to rethink there previous opinion and deciding she wasn't ready yet.
She doesn't hide the fact that she's upset about what Porter did and at first angrily refuses to listen to Porters order to beam the zombie Jane down to earth.(Mrs Stern in all her wisdom decided that because of Porters reckless actions he would have benefit from a little extra responsibility) Dr. Cassabi then tells Denise that she should listen to Porter and orders her to his office were he lectures her. Later Denise reveals to Porter she only kept the Zombie Jane around because it was the only thing that somehow resembled a friend to her. Porter then tells that he didn't like what he did (beaming up with the zombie clone)and assures her that he is her friend.
Denise recently has been changed back into a human. It was mentioned that before Denise became stuck in the raccoon puppet, she had a boyfriend named Lex who she wrote a song for. Denise is the newest Angel-In-Training roaming the halls of Bennett High. Feisty and quick on her feet, Denise wants to earn her wings before Porter earns his - and will go to any length to make sure it happens.
New to the ways of AIT magic, Denise sometimes has trouble following the rules and misuses her magic. Denise's magic often has flaws or consequences that she fails to acknowledge, such as a ping pong paddle that could slow down time but ended up trapping Carl in a slowed time dimension. Another one of her magical mess ups was when she turned Carl into "Carlie" for being inconsiderate on their first date. However, when Denise attempts to change Carlie back to Carl, her magic does not work and they learn that Carl must fully understand what it means to be a girl before he can go back to being a boy. Denise spends most of the episode, beaming away from Porter and enjoying Carlie's misfortune. To show Denise how Carlie feels, Porter turns her into "Denny".
Denise has a crush on Carl and often wants to assist Carl. Her attempts to help, often annoy Porter as Carl is his assignment. Denise usually tries to assist Carl by giving him a magical item (Such as a ping pong paddle) or rescuing him (From a slowed time dimension or Alex's dream). Before she became a raccoon, Denise had a boyfriend named Lex who she presumably broke up with after he never tried to contact while she was stuck in the body of Dennis. Denise seems to like writing and performing songs. She wrote a song for Lex and attempted to write one for Carl but she found it hard to find words that rhyme with "Carl".
Denise's crush on Carl is a recurring theme throughout Season 2. Porter is the only character who seems to know about her crush on Carl even though Denise doesn't hide it very well.Also in a recent episode (I Kinda always knew you'd be my Lex Boyfriend) Mrs Stern finds out Denise and Carl are dating due to the fact that they accidently reveal it because they think that Mrs Stern is the disguised form of Denise's ex boyfriend Lex (who still has feelings for Denise). After that Denise and Carl make a brave and admirable stand for there love in front of Mrs Stern after which she still coldly states its against the rules and that she will put a stop to it (if you cant find love yourself why not destroy someone else).
The act off putting a stop to it comes in the form of a spell she casts on Carl and Denise which will reveal when they have romantic feelings for each other by having them turn blue. If a full alert was ever coming a silent alarm would go off and Mrs Stern would come down to earth to take Denise away from Earth forever and she would never be able to earn her wings and become a full angel. Denise and Carl are to not see each other for a while and they are beamed away by Mrs Stern. Devastated by the sudden dark twist off events Porter has to convince Carl to hold on after Carl states how it hurts a lot and he would have a easier time forgetting Denise if her face didn't appear everywhere.
At that moment Denise beams to were Porter and Carl are and feel Carl's face to see if his real and not just another appearance of him she see's everywhere. Porter then tells Denise and Carl disgusting little things of each other. After he did this Porter figures out that its all Lex doing and the three hatch a plan to extract there revenge. Porter meets up with Lex and persuades Lex to transform into his disguise of Mrs Stern. Porter acts impressed which presses Lex into stating how he can also impersonate her voice. While Lex does her voice Carl and Denise beam to the spot and kiss activating the full alert off the emotion relevance spell. As Mrs Stern beams down to Earth to take Denise away from Earth forever she notices her imposter and forces the imposter to reveal his true form. Shocked to see Lex being able to transform into a full angel(and doing a very bad impersonation of Mrs Stern which she was probably even angrier about.)
She then tells Lex that she came down to Earth to permanently break up Denise and Carl but that a A.I.T. transforming into a full angel is a worse crime then a Angel-Human Relationship. A. Mrs Stern prepares to beam Lex up to Heaven to punish him. Just before Mrs Stern beams Lex and herself up Lex tells Denise to call her after which Denise replies never while i still live (and Denise is immortal so guess how many times she will call Lex). Before Mrs Stern leaves she looks fouly at Porter for laughing at Lex bad impersonation of Mrs Stern she tells Denise and Carl that they will not be punished but that she will be watching them and then beams away.
Porter say that they have to come up with something quick as Mrs Stern will return soon. Carl asks for some privacy with Denise and Porter beams away. Denise tells that she doesn't want to choice between being with Carl and being able to become a full angel some day. Carl replies that she doesn't have to make a choice as he already made it and he choices to not date Denise anymore as he want her to get a assignment and one day earn her wings. Carl then says goodbye and walks away.
He asks Denise to turn her head away from him as his scared that he might look back. As he is nearing a door he cant help himself and looks behind and at the same moment Denise does the same thing showing a small blue glow in both there faces due to the spell implying how the love between Denise and Carl is down but not dead.