The 15 best episodes of The Flash

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When Harry Met Harry... — Katie Yu/The CW

To celebrate all things The Flash, EW looks back at 15 of the speedy drama's installments that best remind us why we love the show; from psychic gorillas to time travel, and all of the comic book goofiness in between.

15. "Pilot" (Season 1, Episode 1)

The Flash's series premiere remains one of its strongest episodes by virtue of the fact that it's the one that started it all. Building off of the goodwill that Grant Gustin earned with his debut as Barry Allen on Arrow, the pilot is confident and bold. The episode introduces us to easily lovable characters, including Iris West (Candice Patton), Joe West (Jesse L. Martin), and Harrison Wells (Tom Cavanagh). It's kind of insane how the show continues to refer to elements that were first teased in this episode, like Grodd, the future newspaper, and more.

14. "Luck Be a Lady" (Season 4, Episode 3)

Written by Sam Chalsen and Judalina Neira, "Luck Be a Lady" was emblematic of season 4's attempt to raise the fun quotient after the depressing third season. Team Flash goes up against Becky (Sugar-Lyn Beard), a.k.a. Hazard, a metahuman who could give others bad luck, which led to some clever, Rube-Goldbergian set pieces that differed from the show's typical form of spectacle.

13. "Elongated Journey Into Night" (Season 4, Episode 4)

In Elongated Man's (Hartley Sawyer) debut episode, director (and star) Tom Cavanagh swerves into the humor of Ralph Dibny's stretchy powers—the sight of Ralph's elongated nose is beyond hilarious—making this one of the show's funniest episodes. Plus, Danny Trejo guest-stars as a murderous bounty hunter/overprotective father!

12. "Enter Flashtime" (Season 4, Episode 15)

After a nuclear bomb goes off in Central City, Barry has no other option but to enter Flashtime—which means he's traveling so fast that a few seconds can be stretched out into minutes—while he and several other speedsters look for a solution. Sure, the setup was a little gimmicky, but Todd Helbing and Sterling Gates' script and the cast's performances punctuate the spectacle with some great emotional beats; from Killer Frost (Danielle Panabaker) expressing her concern for Caitlin to Harry (Cavanagh) opening his mind to Jesse (Violett Beane) and sharing his memories of her mom with her.

11. "Killer Frost" (Season 3, Episode 7)

After using her powers to save Barry from Savitar, Caitlin loses control and goes full-on Killer Frost, creating more turmoil for Team Flash. As Killer Frost threatens her friends' lives, Joe (Martin) desperately tries to save Wally, and Barry is forced to confront some of his recent mistakes. Seeing the team at odds like this was hard, but it was emotionally fulfilling and necessary.

10. "The Man in the Yellow Suit" (Season 1, Episode 9)

The climactic season 1 midseason finale juggled Flash confronting Reverse Flash for the first time, Cailtin and Cisco's (Carlos Valdes) search for the Firestorm Ronnie, and Barry telling Iris how he feels without missing a beat. Furthermore, it delivered several surprises that eventually land four years later.

9. "Welcome to Earth-2" (Season 2, Episode 13)

In the season 2 premiere, The Flash promised to take viewers around the multiverse, and it delivered on that with "Welcome to Earth-2." Barry and Cisco travel to Earth-2 and meet their doppelgängers. The differences between the Earths were intriguing, and Panabaker, Valdes, Patton, and returning guest-star Robbie Amell turned in over-the-top performances that were a blast to watch.

8. "Grodd Lives" (Season 1, Episode 21)

Two words: Psychic gorilla. The Flash's pilot teased the eventual introduction of Gorilla Grodd (David Sobolov). However, it was easy to remain somewhat skeptical about whether or not the show would actually follow through, given that it was working within the bounds of network television. Luckily for us, it gave us an epic fight between the Flash and Grodd that did not disappoint.

7. "Tricksters" (Season 1, Episode 17)

The Flash, like most of the Arrowverse shows, has always been good about honoring the past. This episode is no exception, and guest-starred Mark Hamill as the Trickster, the role he played on CBS' 1990 Flash series. Hamill's performance is thrilling and just a touch scary. Beyond the fan service, the episode explores father-son relationships and contains a classic Flash moment: Harrison Wells/Eobard Thawne's breathtaking Speed Force speech.

6. "Duet" (Season 3, Episode 17)

Featuring a mix of covers and original music, the Flash-Supergirl musical crossover is a blast of joy right to the brain. After being whammied by the Music Meister (Darren Criss), Barry and Kara (Melissa Benoist) find themselves trapped in a movie musical and have no other option but to move through the plot to the end, which leads to some gloriously fun and heartwarming numbers. Tunes include Victor Garber, Jesse L. Martin, and John Barrowman's rendition of "More I Cannot Wish You" and Gustin and Benoist's duet, "Super Friend," which was written by Crazy Ex-Girlfriend's Rachel Bloom. Sure, the way everything is resolved is rather corny, but that's part of its charm.

5. "Flash vs. Arrow" (Season 1, Episode 8)

Oliver Queen (Stephen Amell), Diggle (David Ramsey), and Felicity (Emily Bett Rickards) visited Central City while investigating a murder, crossing paths with Team Flash. Of course, this led to the Flash and the then-Arrow throwing it down in the street after the former gets whammied. The Arrowverse's first proper crossover event captured the fun of classic comic events, set the stage for the future success of "Invasion" and "Crisis on Earth-X," and made Barry and Oliver's relationship the bedrock of the entire universe.

4. "Going Rogue" (Season 1, Episode 4)

The greatest gift The Flash has given us is Wentworth Miller's perfectly campy portrayal of Leonard Snart, a.k.a. Captain Cold. Almost no one else on this show has as much fun as Miller does while he's playing this cold and calculating thief, and that was apparent from his first episode, which remains a classic. Of course, Miller's performance would only improve once his Prison Break partner-in-crime Dominic Purcell joined him as Heat Wave.

3. "Out of Time" (Season 1, Episode 15)

"Out of Time" is an insane episode that starts with an awkward bowling double date and ends with Barry running so fast to stop a tidal wave from destroying Central City that he accidentally time travels. There's a huge gulf between those two places, but the episode successfully bridges them and gives us tons of other memorable moments along the way; from Iris learning Barry's secret, to seeing the Weather Wizard's (Liam McIntyre) powers in action, to the haunting and heartbreaking scene that Valdes and Cavanagh share in S.T.A.R. Labs. So much of this episode beyond the time traveling just sticks with you once you see it.

2. "The Runaway Dinosaur" (Season 2, Episode 20)

This episode shouldn't have worked. But, somehow, director Kevin Smith, writer Zack Stentz, and the entire cast pull it off, giving fans one of the show's most heartfelt hours ever. Partially set in the Speed Force, it finds Barry trying to make his way back home after being sucked into the mysterious source of his power. The story juggles explaining how the Speed Force works while also telling a poignant story about grief and acceptance. While all that is happening, there's a zombie running around S.T.A.R. Labs.

1. "Fast Enough" (Season 1, Episode 23)

Yes, it's sort of cheating to make a season finale number one on a list, but no episode better represents what the show does best. By this point in The Flash's run, everyone knows it's built on the pillars of heart, humor, and spectacle, and "Fast Enough" scores a 10 on all three points. The heart comes from, well, almost every conversation Barry has in the episode; Cavanagh and Valdes bring some laughs with their performances, while the journey back to the night Barry's mom died and the subsequent wormhole that opens above the city are the spectacle. Every part of the show was firing on all cylinders in this episode, and to this day, The Flash is still trying to reach this mark.