She pretended to be Diane, Dave's ex-girlfriend. Dave's mother claimed she didn't have to thank her as she was paying her. To add further shock, it's revealed that Nikki isn't a woman at all, but a man named Nicholas LaPorte.
In part 1 of The Wedding Frame, she is in her trailer home as she is brushing her teeth. She gets a phone call from someone saying that she will find a manila envelope on her front porch. She is taken aback by the word manila. The person explains what manila is and tells her the envelope contains the information for her assignment. After the conversation, she sees the envelope and it's a picture of Dr. Dave. The next day, she calls Noelle and says she's on her way to Sheltered Shrubs. Nikki asks if Noelle can accommodate her and Noelle agrees. She asks Nikki how long she will be in town. Nikki says just long enough to pop in on an old friend's wedding. Monster shows up out of the woods and Nikki narrowly avoids hitting him. Later that night, she pulls up her trailer into a mobile home lot. Buzz notices her outside and decides to go over and introduce himself. Nikki is inside writing down her plan with Monster laying in a dog bed. She answers the door and Monster escapes. Buzz thinks he will come back. He then notices a picture of Lois in her hand.
In part 2 the next day, Nikki disguises herself as Diane and says hi to Dr. Dave as he tries to find the right place for his honeymoon with Lois. He steps out for a moment and talks to "Diane". Dave tries his best to console her after she gets upset about hearing he's getting married. They both have a cup of coffee and catch up on some old memories. At the camera shop next door, Jonas sees him and "Diane" talking. She pretends to fall over and Dave catches her. Jonas notices this and takes a picture of them.
In part 3, she shows up at the bakery with the secretary, and Mrs. Dave where Myrna put something in Lois' slice of cake and made her fall asleep. Mrs. Dave puts Lois' engagement ring on Nikki's finger. Mrs. Dave takes out a camera and offers to take pictures of Nikki looking surprised as if her son had proposed to her. Nikki tries her best to look surprised after Mrs. Dave wants her to look more convincing. Mrs. Dave gives Nikki her money without thanking her. The next day, "Diane" shows up at the wedding. Hoodsey notices her and tells Carl. "Diane" gets up and shows the picture of her and Dave. Carl and Hoodsey try to say she is really Nikki LaPorte. Noelle intervenes and brings the real Diane Francis to the wedding. She then exposes Nikki is really a man with the name Nicholas. Monster comes in a greets Carl. Nicholas recognizes him after saving him from the street. Carl claims that Monster is his.
He is willing to do any dirty work that is required of him. He can be very convincing as a female. He seems to have very little morals.
In part 1, he wore a light pink top and a dark pink skirt with yellow high heels. When he disguises himself as Diane, he wears a blonde wig, a red dress and white high heels. At the wedding, he wears a dark green dress.
Mrs. Dave: She made a deal to wreck her son's wedding by disguising as Diane. She doesn't seem to be as close to him as she is with Myrna and Maryellen. Mrs. Dave didn't bother thanking her after she paid him.
- It's unknown how much he and Mrs. Dave have known each other. She probably calls on him for favors every now and then if she is in a predicament.