'The Flash': Easter Eggs and Pop Culture References in "The Elongated Knight Rises"

Harley Quinn

As we've already speculated about, it feels like tonight's episode made some pretty sly references to another DC antihero, Harley Quinn.

Prank initially breaks Axel out of jail by using tainted pudding, a food that coincidentally serves as one of Harley's biggest catchphrases. As the episode goes on, the parallels between Prank and Harley only seem to continue, with her relationship with The Trickster (Mark Hamill) being presented as very Joker-esque, and with Prank mentioning that she's off her meds.

Considering the fact that Prank was created before Harley -- and the long history the Arrowverse has of attempting to bring her to screen -- these references do feel at least somewhat intentional. And even if they're not, they're a fun added layer to bring to the episode.

Mr. Fantastic

The episode opened with Ralph Dibny/Elongated Man (Hartley Sawyer) attempting to stop a hostage situation. When the hostage taker asked what to call Dibny, he froze, realizing that he didn't officially have a superhero name yet.

As he did, it almost sounded like he mumbled "Mister", which would serve as a pretty sly nod to Mr. Fantastic, Marvel's resident stretching hero.

This certainly wouldn't be the first subtle Marvel reference that The Flash has thrown in this season, between the nature of Barry's return and the already-iconic "Council of Wells". But still, like the Plastic Man nod that occurred earlier this season, it shows just how difficult it was for Ralph to find a good name.

'Alien'

When the group is trying to determine how to defeat Axel and Prank's bright pink acid, someone compares the substance to "xenomorph blood."

As fans of the Alien movies know, xenomorph blood is pretty acidic, with the ability to burn through basically any substance. But we have to admit, the franchise would be completely different if that blood was the same bright pink.

Fall Out Boy

When Ralph and Axel officially faced off, Ralph delivered a pretty clever critique of the villain's costume, referring to him as "Fall Out Boy."

This, of course, is a nod to the beloved punk-pop band, who has previously gone through some colorful aesthetics in the past.

Hey, if anything, this confirms that Fall Out Boy are still somewhat of a thing on Earth-1, after Oliver Queen pondered exactly that while catching up on pop culture in Arrow's first season.

Stretch Armstrong

Axel and Ralph refer to each other quite a bit throughout the episode as they're attempting to figure out how to outsmart each other. At one point, the villain refers to Ralph as Stretch Armstrong, a reference to the iconic (and slightly upsetting-looking) toy.

Thankfully, that reference has become a bit more current in recent years, thanks to a comic series from IDW, as well as Netflix's Stretch Armstrong and the Flex Fighters cartoon.

Beebo

As we've also already mentioned, tonight's episode saw the return of a Legends of Tomorrow fan-favorite: Beebo.

The cuddly stuffed animal appeared in Legends' midseason finale, which was aptly-titled "Beebo The God of War." In the episode, the Legends traveled to Viking-era Scotland, where they found Beebo being worshipped as a sort of Norse God.

The Legends ultimately turned things to normal (while doing away with the awesome-sounding holiday of "Beebo Day"), but the toys themselves still existed within the present-day Arrowverse timeline. But for those who have taken a liking to Beebo -- namely, fans who frequent the Arrowverse's various subreddits -- it's safe to say that this The Flash cameo is a little unexpected.

Oregon Trail

And finally, tonight saw the unexpected return of the "Mystery Girl" (Jessica Parker Kennedy), who sparked quite a lot of speculation when she appeared at Barry and Iris' wedding.

Mystery Girl ran into Cisco and Ralph at Jitters, striking up a conversation about who should pay for their coffee. Cisco then noticed Mystery Girl's t-shirt, which featured the 8-bit version of the ox and cart from Oregon Trail.

The beloved video game, which initially came out in 1971, is instantly referred to as a "classic" by Cisco and Mystery Girl. But depending on who the girl actually is (and what time period she hails from), it could really be a classic for her.