Warning: SPOILERS for The Flash season 7, episode 6, "The One With the Nineties."
While The Flash is often filled with referential humor, the season 7 episode "The One With The Nineties" took this to a new level, with an storyline that sent engineers Chester Runk and Cisco Ramon on a trip back in time to 1998, filled with pop culture references and Easter eggs. The episode paid homage to many classic movies and TV shows of the era, as "Team Chessco" tried to unravel the paradox and find a way home.
The plot of The Flash season 7 has centered around the discovery of several new Forces following the rebirth of the Speed Force. With Barry Allen placing himself in a coma to recover and the Speed Force itself having taken the form of Barry's mother as it healed from its own injuries, the rest of Team Flash began looking for ways to track the new Forces that seemed to want to destroy the Speed Force. This led to the discovery of a new third Force tied to the time stream and an increasing number of anachronisms around Central City.
Beyond traveling back in time, Cisco and Chester also found themselves watching the same day play out repeatedly. This led to the two pretending to be high school students, as they tried to track the being responsible around Masonville High School and hijinks ensued, with a number of relevant references coming into play.
Friends
Even the title of The Flash season 7, episode 6 is a reference to the Nineties and the naming convention of one of the decade's most popular sitcoms; Friends. Every episode of Friends after the pilot had a title that started with the words "The One With" or "The One Where," such as "The One With The Dozen Lasagnas" and "The One With Rachel's Crush." The Flash's "The One With The Nineties" also opened at CC Jitters; the preferred coffee shop of Team Flash. Nearly every episode of Friends featured at least one scene of the ensemble hanging around their favorite coffee shop, Central Perk.
Jurassic Park
The opening scene of "The One With the Nineties" centered around Natalie, a barista at CC Jitters and Chester Runk's not-so-secret crush. As Natalie got off work and complained to a friend on the phone about how boring her job was, a man in Roman armor ran past her and a submarine suddenly manifested in the middle of the street. While this was fairly typical for Central City on a Tuesday night, it was a sudden ripple pattern in her coffee which made Natalie freeze up, just before a Tyrannosaurus Rex stomped into view and growled at her. While comedic in tone, the scene was a send-up of one of the most dramatic moments of Jurassic Park.
Under The Dome
"The One With The Nineties" found Cisco Ramon and Chester Runk installing signal-boosting scanners around Central City and its suburbs, to better detect The Flash's new cosmic forces unleashed in the wake of the Speed Force's rebirth. One of these new powers, a green wave that left behind residual traces of temporal energy, seemed to make Chester and Cisco's phones disappear along with their van, while they were on the outskirts of Masonville. When they encountered a forcefield that prevented them from leaving the town, Cisco declared they had been "under-the-domed" in a nod to Under The Dome; the 2013 series based on the 2009 book by Stephen King.
Blockbuster Video
Upon reaching Masonville, Chester and Cisco figured out that they had traveled in time based on one simple fact; the local Blockbuster Video was still open and guaranteeing that they would have Space Jam in stock. The video store also had movie posters promoting the romantic drama Why Do Fools Fall In Love?, the supernatural murder mystery Fallen, the science fiction thriller Sphere and the romantic fantasy comedy Practical Magic - all of which were released in 1998.
Space Jam
Apart from being the most prominently featured film on the marquee at Blockbuster Video, the 1996 movie Space Jam also was mentioned when Cisco and Chester were confronted by the villain of the episode. Still playing the part of high school students, our heroes played innocent and tried to make their escape, saying they were thinking of heading over to Blockbuster and checking out Space Jam. (This may be a clever bit of corporate synergy on the part of Warner Bros., as the first trailer for Space Jam 2 dropped the same week this episode of The Flash originally aired.)
Groundhog Day
Another famous Billy Murray movie besides Space Jam played a prominent role in the plot of "The One With the Nineties," with The Flash episode also acting as a tribute to the 1993 comedy Groundhog Day. In addition to being sent back in time, Chester and Cisco quickly determined that the same day, December 4, 1998, was replaying over and over within the town of Masonville. While this was ultimately unconnected to the reasons for the time loop, the paradox did give Chester a chance to bond with the father he thought had abandoned him as a child and work out some of his issues, in the same way that Bill Murray's miserable weatherman character became a better person after repeating the same day over and over. The episode gave Bill Murray himself a nod in a subtle bit of foreshadowing, as the two time-displaced scientists walked past a billboard for Murray Motors just before realizing they had become lost in time.
Hot Tub Time Machine & Back To The Future
After realizing that they had traveled back to 1998, Chester asked how they were supposed to get home "without a DeLorean or hot tub." This evoked the two time machines from the Hot Tub Time Machine and Back To The Future franchises, respectively. "The One With the Nineties" also paid homage to Back To The Future with Cisco and Chester's entrance to Masonville mimicking Marty McFly's arrival in the Hill Valley of 1955, with a walk around the town square confirming the protagonists had traveled back in time.
DJ Jazzy Jeff and The Fresh Prince
To better blend in among the denizens of Masonville High School as they searched for the metahuman responsible for the time loop, Chester and Cisco raided the school's Lost and Found and picked up some clothes more appropriate to the late Eighties or early Nineties than 1998. Their outfits resemble the colorful neon garb and wild patterns favored at that time, but which were perhaps most famously worn by DJ Jazzy Jeff and the Fresh Prince (aka Jeffrey Allen Townes and Will Smith) in the classic Nineties sitcom The Fresh Prince of Bel-Air. The whole situation also seems to be a parody of the tradition of shows aimed at teenagers casting actors who were clearly in their 20s and 30s as teenagers.
The Matrix
Cisco accidentally uncovered the time loop while reassuring one suspicious teenager that he and Chester really were teenagers who also "like Beanie Babies and The Matrix." When the teen suddenly looked dazed and said that The Matrix hadn't come out yet, Cisco asked how he knew that just before the time loop was reset. In fairness to Cisco, he was only off by a little bit in his efforts to be timely, as The Matrix was originally released on March 31, 1999 - about four months after the ever-repeating December 4, 1998 he was trapped in. "The One With the Nineties" is also something of a tribute to The Matrix, as both stories deal with people trapped in an artificial reality.
Steve Urkel
The villain responsible for time loop was ultimately revealed to be Deon Owens; an embittered ex-athlete whose promising career in professional football was ended by an untimely injury in the first quarter of the state high school football championship. Empowered by what Cisco later dubbed the Still Force, Deon created his own personal heaven, reliving what had been the best day of his life repeatedly and dragging the rest of Masonville along for the ride, much like Scarlet Witch in Wandavision. When Deon finally discovered the two scientists who had been disrupting his paradise, he said he was going to "kick you wannabe Urkels to the curb." This was a reference to nerdy Nineties icon Steven Urkle, who became the breakout character of the sitcom Family Matters after what was meant to be a single guest appearance.
Retro Fashion Flashbacks
Outside the Masonville dome, the Still Force was causing random fluctuations in the time stream, with objects from other times (such as the T-Rex that menaced Natalie) being pulled into the present and existing objects being altered at random. This resulted in all of the allies of Flash who were at STAR Labs having their clothes changed, with Detective Joe West suddenly sporting a zoot suit and fedora, Frost rocking a new Hippie look and Caitlin Snow suffering a very Eighties hair-do with matching power suit and heels. Iris West-Allen had the best entrance, however, walking into the command center like the second coming of Pam Grier, as a blaxploitation music sting flowed into the soundtrack.