When Arrow debuted on The CW in 2012, no one had any idea how large the universe of that show would eventually become. Where the series’s network predecessor, Smallville, had avoided the more comic book-y elements of the Superman mythos for as long as possible, Arrow embraced those elements almost immediately, putting Oliver Queen in a costume and even giving him a catchphrase in the very first episode. The Arrowverse has since grown to include four different series across two different Earths, and has become a place where superhumans, aliens, time travel, and parallel worlds are all commonplace.

Just as crossovers and team-ups in comics are a hallmark of characters operating in a shared universe, crossovers between the Arrowverse shows and characters have become an annual event, often used to set up future stories or series, and always a lot of fun. With the most recent crossover, “Elseworlds,” having just wrapped earlier this week with a tease for what is sure to be the biggest Arrowverse crossover yet, we thought we’d take a look back at all of the times that Green Arrow, The Flash, Supergirl, and the other heroes of the Arrowverse have joined forces, and see how they stack up against each other.

Honorable Mention: Worlds Finest (Supergirl S1E18)

While technically not a full Arrowverse crossover, this was the first cross-Multiverse superhero team-up. It also happened to be cross-network, as Supergirl was still on CBS when Grant Gustin’s The Flash popped over from Earth-1 by mistake while trying to up his speed game to take on Zoom, and he and Melissa Benoist’s Girl of Steel had their first team-up. Where most team-ups between heroes usually begin with a misunderstanding and battle between the two heroes, the instant rapport between Gustin and Benoist in this episode made the team-up feel extra-special, and it would set the stage for Supergirl’s eventual official entry into the Arrowverse crossovers once the show jumped from CBS to The CW. Plus, it birthed this wonderful scene of Kara’s delighted reaction to Barry fetching everyone in the room ice cream as a demonstration of his superspeed, so it had to make an appearance.

Honorable Mention: Duet (The Flash S3E12)

Again, not a full Arrowverse crossover, but another cross-Earth caper involving The Flash and Supergirl, plus guest-stars including Legends of Tomorrow’s Victor Garber and Arrow’s John Barrowman. After an alien called The Music Meister hypnotizes Supergirl into a coma and escapes to Earth-1, Mon-El and J’onn J’onnz follow him in the hopes that Team Flash can help revive Kara. Unfortunately Barry is also whammied by The Music Meister, and he and Kara end up having a shared 1930s gangster/musical hallucination featuring members of each of the shows’ casts plus the aforementioned guest-stars. The Arrowverse is filled with actors who’ve appeared on Broadway (Jesse L. Martin, Carlos Valdes, Jeremy Jordan, plus Garber and Barrowman), while Gustin and Benoist were both cast members on Glee, and both are trained dancers. The end result is arguably the highest-quality musical episode of a non-musical series ever made. Duet includes numbers from the songwriting teams behind La La Land and Crazy Ex-Girlfriend, and it’s really just a delight.

#5: Legends of Today/Legends of Yesterday (The Flash S2E08/Arrow S4E08)

This was the second crossover for the Arrowverse, and served primarily as set-up for the then-upcoming Legends of Tomorrow spin-off series. Several key characters from that series are introduced, including Kendra Saunders officially becoming Hawkgirl, and the first appearances of both Carter Hall/Hawkman and the immortal villain Vandal Savage, who would go on to be the Big Bad of the first season of LoT. The story here is pretty straightforward: Vandal Savage wants to kill Kendra, as he has done to incarnations of Kendra and Carter numerous times throughout the millenia, and he’ll destroy Central and Star Cities if The Flash and Green Arrow don’t hand her over to him. It’s an entertaining tale, though some of the set-up for LoT is pretty clunky. It’s also significant as the first appearance of Oliver’s son, William, whom he meets when he runs into an old girlfriend in Central City. William has become a regular character on Arrow, with a future version of the character currently appearing in the seventh season’s flash-forwards.

#4: Elseworlds (The Flash S5E09/Arrow S7E09/Supergirl S4E09)

I won’t go into too much detail about “Elseworlds,” as it just wrapped up earlier this week, and you can read full recaps for each episode elsewhere on the site. There’s a lot to love about this crossover, from the incorporation of Earth-38’s Superman and the introduction of Lois Lane, to the first appearance of Gotham City and of Ruby Rose as Kate Kane/Batwoman, to the brief appearance by John Wesley Shipp, reprising his role of The Flash from the early ‘90s TV series. Ultimately, though, this three-parter was basically all setup, either for the in-development Batwoman spin-off series or for next year’s “Crisis on Infinite Earths” crossover. It was a fun event, but not really substantial enough to rank higher on the list.

#3: Flash vs. Arrow/The Brave and the Bold (The Flash S1E08/Arrow S3E08)

Barry Allen first appeared during the second season of Arrow before becoming The Flash the following year, and Oliver Queen put in an appearance in the pilot episode of The Flash, but this two-parter was the first official crossover between Arrowverse shows, and the first time that the teams from the two series met each other. It’s also unique in that each episode, while loosely connected, largely stands on its own as a self-contained story. The first hour has Oliver Queen travelling to Central City to help Team Flash take down a reimagined Rainbow Raider, who used his Psycho-Pirate-like power set to brainwash The Flash into fighting Arrow. The second half saw Barry Allen in Starling City to help Team Arrow against classic Flash foe Captain Boomerang. These two episodes went a long way towards cementing the brotherly relationship between Oliver and Barry, and established the two as equals for the first time.

#2: Invasion! (The Flash S3E08/Arrow S5E08/Legends of Tomorrow S2E07)

The third Arrowverse crossover was the biggest one yet, incorporating not only Teams Flash and Arrow, but the time-traveling Legends of Tomorrow as well. The story also brought Supergirl to Earth-1 for the first time, recruited by The Flash to help the other heroes against the invading Dominators. The story is loosely based on the 1989 Invasion! miniseries, with added time-travel elements for good measure. As alien invasion stories go it’s entertaining enough, but the way it incorporated the ongoing elements from the three series really elevates it. Season 3 of The Flash began with Barry creating the Flashpoint timeline, and this crossover revealed the impact that his altering of history had had on all of the characters in the Arrowverse—his timeline shenanigans is actually what caused the aliens to invade—and resulted in some comeuppance for the scarlet speedster. The middle, Arrow installment was also the 100th episode of that series, a “For the Man Who Has Everything”-esque story in which a Dominator-abducted Team Arrow get a glimpse at life without all the superheroics. As a result the overall crossover is somewhat disjointed tonally, and I was tempted to rank this one below “Flash vs. Arrow”/”The Brave and the Bold,” but ultimately the ambition of the story, and the way that it advanced the storylines for all of the characters involved, elevates this crossover on the list. It also acknowledged Brandon Routh’s time as Superman with a throwaway line about Supergirl that delighted me to no end the first time I watched it.

#1: Crisis on Earth-X (Supergirl S3E08/Arrow S6E08/The Flash S4E08/Legends of Tomorrow S3E08)

This one has everything: weddings, hook-ups, Nazi superhero doppelgangers from an alternate Earth, complicated surgeries, heroic sacrifices, and actual stakes. Everything was big about this crossover, from the presentation (two episodes a night for two subsequent nights) to the episode structure (individual episodes forwent their own title cards, instead using “Crisis on Earth-X” as the title), to the fact that, unlike the other crossovers, every character from every series is in every episode. More than any other Arrowverse crossover, “Crisis on Earth-X” is essentially a four-hour movie featuring every hero on Earth-1 (plus several from Earth-38) united against invading forces from the Nazi-controlled Earth-X, who have recently discovered how to travel through the Multiverse and have decided that conquering the other Earths is the best use for such technology (Nazis, am I right?). This crossover would have major consequences for the three Earth-1-based series: Professor Martin Stein, one-half of the Legends of Tomorrow’s Firestorm, would lay down his life in order to save Earth-1, while both Barry Allen & Iris West and Oliver Queen & Felicity Smoak ended up marrying at the crossover’s end. Earth-X’s Ray Terrill, aka The Ray, who was introduced in this crossover, would star in his own animated series on CW Seed, while his husband, Leo Snart (an alternate version of Earth-1’s Captain Cold), would briefly join the Legends of Tomorrow. The initial installment of the story also featured the first appearance of a mystery girl who would eventually be revealed to be Nora Allen, Barry and Iris’s daughter from the future, who has become a series regular with The Flash’s fifth season. I really wasn’t kidding when I said this crossover had everything. One hopes that next year’s “Crisis on Infinite Earths” can follow the example set by this Crisis.