Certified Crowning Music Of Awesome: Carly Simon won an Oscar, a Golden Globe, and a Grammy for "Let the River Run". At the time it was the only song ever to win all three awards. As of 2011, the only other song to achieve this was "Streets of Philadelphia" by Bruce Springsteen.
The Actor Swap Is Coming...: Harrison Ford and Alec Baldwin are the two male leads in this film. Less than three and a half years after Working Girl, both actors had played CIA analyst Jack Ryan in separate adaptations of Tom Clancy novels.
Dawson Casting: A very borderline example of this trope. When Tess and Katharine first meet, Tess has just celebrated her 30th birthday a few days earlier, while Katharine is turning 30 the following week. Melanie Griffith was actually 30 at the time of filming, but Sigourney Weaver was 38. However, the fact that Weaver's character seems much older than she is in comparison to Tess is intentional. Or Katherine could have been lying about her age.
Doreen is Joe Pesci's girlfriend at the Copa in Goodfellas. She's the one who almost gives Pesci a heart attack when she talks about how a girl could find a talented black singer like Sammy Davis Jr. attractive.
David Duchovny: Working Girl was his first ever film credit. Look for him in the back of the closet in the upper left at Tess's surprise birthday party. See him again in the credits billed as one of four "Tess's Birthday Party Friends".
Oliver Platt: Tess's coworker Lutz from early in the movie, in only his 3rd ever movie credit.
Kevin Spacey: Coke-snorting Bob Speck from Arbitrage. Spacey was a last-minute replacement to play the role, being picked up in the limo with a copy of the script on the back seat for him to learn on the way to the shoot. He had a recurring role on the 1980s crime drama Wiseguy at the time, but mostly was doing bit parts in movies and one-off roles on other TV shows.
Joan Cusack as Tess's friend Cyn. Cusack was coming off the heels of her only season of Saturday Night Live (during a season that nearly got the show canceled due to low ratings and bad reviews), as well as appearing in a few bit parts in other movies. She has worked steadily ever since in television and movies, including Toy Story 2 and 3, in which she provides the voice of Jessie the Cowgirl.
Nora Dunn as Ginny. This was the first movie Dunn ever appeared in. She was best known at the time for being a current regular on Saturday Night Live (and also being in the same cast as Joan Cusack, though, unlike Cusack, Dunn was popular and funny enough to stay on the show when it was being revamped for its 12th season). Dunn was on SNL from 1985-1990, where she was fired for refusing to appear in an episode hosted by misogynistic shock comedian Andrew "Dice" Clay. From then on, she's been in minor TV and film roles (for those who watch 1990s cartoons, you might know her as the voice of Histeria!'s meddlesome network censor, Lydia Karaoke).
Olympia Dukakis as the Personnel Director for Petty Marsh, who ends up placing Tess with Katharine Walker. Dukakis was most famous at the time for winning the Oscar for Best Supporting Actress playing Cher's mother in Moonstruck the previous year, and for being the cousin of 1988 Democratic Presidential Nominee Michael Dukakis. She went on to play roles in Steel Magnolias, the Look Who's Talking movies, and Mr. Holland's Opus.
A 19-year-old Ricki Lake as a bridesmaid at the Trask wedding. She's only on screen long enough to point out fellow bridesmaid "Bitsy" to Harrison Ford. Earlier in 1988 she played the lead role in John Waters' Hairspray, and went on to a long and steady career in television, including a eleven-year run as a talk show host.