Under pressure of the paying public Ellery had to get more and more romantically involved. This seemed especially important since they wanted to make it in Tinseltown.

It was through radio that Nikki first truly came alive. Introduced in "The Adventure of the Gum-Chewing Millionaire" (Jun 18. 1939), she was immediately characterized as a “blonde professional typist.” The radio story "The Adventure of the Lost Child" (Nov 26. 1939) states Kansas City as the place where Harvey Morrell, an old friend of her family, came from. In The Last Man Club (1941), based on one of the early radio episodes, she’s described again as “pert, blonde and pretty,” living on West 94th Street (20). Her radio presence made perfect sense: a female voice added tonal contrast and character to the medium, not to mention the romantic chemistry she sparked with Ellery. Radio also allowed Nikki to become a regular fixture long before she made her relatively late debut in the printed stories.

Yet Nikki Porter was never one to be pinned down. Each time we meet her—be it in radio, print, or film—her backstory and even her appearance shift. Sometimes she’s blonde, sometimes red-haired, like in There Was an Old Woman (1943), where Ellery also claims not to have met her before the Potts murder. There, she’s “a small slim miss with nice red hair.” and her family is in New York, where she was born. Her original name was Sheila Potts (with her mother's last name) or Sheila Brent (with her father's last name)...and she's extremely wealthy. Despite this "handicap" she accepts Ellery's offer of becoming his secretary (with a salary). Nikki wasn't her real name. She changed it on the advice of Ellery. First he asks her to change her identity to Susie McGargle from Kansas City. - She doesn't like the idea and then Ellery makes a second attempt (after a heroin from one of his books) "... N-i-k-k-i . The last name Dempsey didn't fit... Nikki Jones? Nikki Brown? Nikki Green? Nikki Keats? Nikki Lowell? Nikki Fowler? Yes it had to end with  -er. Parker. Farmer. Porter...Porter. Nikki Porter that's it!"

She also stars in two 1952 Calendar-stories as Ellery’s loyal secretary and companion, and makes her final appearance in The Scarlet Letters (1953), where we learn she spent her childhood in Kansas City—though in earlier radio episodes, her family was placed in New York.

The 1975 Wayne-Hutton TV series Ellery Queen made different choices. The producers opted for Paula Paris over Nikki Porter, despite the show being set in 1947—the heyday of Nikki’s radio career. Instead, Ellery is seen engaging romantically with other characters, such as Jenny O’Brien in The Adventure of Colonel Niven’s Memoirs, and a persistent aspiring author in The Adventure of the Eccentric Engineer. All suggesting his romantic life was fluid and fleeting. These portrayals reinforced the idea that Ellery Queen—like his creators—was not exactly a “ladies’ man.” Dannay and Lee prioritized cerebral plotting over romantic entanglements, which may explain why Nikki and other female characters often played second fiddle.

Nevertheless, Nikki Porter endured in spirit if not always in presence. Whether through name, personality, or role, echoes of her remained throughout the series. And in the eyes of many fans, she was the ideal partner for the ethereal Ellery Queen. No wonder speculation arose over the identity of the mysterious “Mrs. Queen” mentioned by J.J. McC. For many, it could only have been Nikki Porter—a conclusion far easier to accept than solving the ongoing mystery of Ellery’s mother, whose identity remains unknown to this day.