The Flash (2014)

Going Rogue - S1-E4

Trivia: Kahndaq is mentioned heavily in this episode. Kahndaq is a fictional country, home to DC anti-hero, Black Adam.

Crisis on Earth-X, Part 3 - S4-E8

Trivia: Supergirl says to her doppelganger "General, can you step outside." That line was said by Superman in Superman II.

Attack on Gorilla City - S3-E13

Trivia: Julian asks Barry "are you gonna go to the planet of the apes?" Tom Felton played Dodge Landon in the modern remake of that film.

Attack on Gorilla City - S3-E13

Trivia: Before Barry and the others travel to gorilla city, Julian says something about Bludhaven. This is the city of Dick Grayson, aka Nightwing, former partner of Batman as the first Robin.

Trivia: Robbie Amell, who plays Caitlin's fiancee Ronnie, is the cousin of Stephen Amell, who plays the lead role on Arrow.

Elseworlds, Part 1 - S5-E9

Trivia: When Oliver and Barry breach to Earth-38, the transition music is Remy Zero's "Save Me", famous for its use as the theme song to Smallville. Other homages include the same barn used for the Kent farm and Lois calling Clark "Smallville."

Fallout - S1-E14

Trivia: Towards the end when Caitlin and Iris are talking about her cousin they mention Midway. That's the city of Hawkman and Hawkgirl.

Fallout - S1-E14

Trivia: Towards the end Iris asks Caitlin about her cousin and they mention Coast City, the hometown of Hal Jordan, AKA Green Lantern, another DC superhero.

All Star Team Up - S1-E18

Trivia: When The Atom first appears, the characters say "It's a bird" "It's a plane", an obvious reference to Superman, played by Brandon Routh in "Superman Returns", who also plays The Atom in this episode.

Tricksters - S1-E17

Trivia: Mark Hamill plays James Jesse, the original Trickster, a role he also played twenty-five years earlier in the 1990 Flash TV series.

Things You Can't Outrun - S1-E3

Trivia: The movie Barry and Iris are leaving is entitled Blue Devil II. A reference to DC Comics superhero Blue Devil, who was a stuntman that worked on the in-universe "Blue Devil" films.

Elseworlds, Part 1 - S5-E9

Trivia: Elizabeth Tulloch, who plays Lois Lane, is married to David Giuntoli, with whom she starred on Grimm, and who had auditioned to play Clark/Superman in Man of Steel.

Goldfaced - S5-E13

Trivia: Sherloque develops a crush on Renee Adler, a clear play on "Irene Adler" from other Sherlock Holmes media. Although only appearing in one book, in TV shows/movies Irene is frequently a love interest of Holmes.

Jon Sandys

I Know Who You Are - S3-E20

Trivia: When Barry is suffering amnesia he asks to be named Bart, Bart Allen in the comics is grandson of Barry and the future Flash.

Crisis on Earth-X, Part 3 - S4-E8

Trivia: The outfit wore by Snart is the classic costume including the visor from the comics and the cartoon TV show.

Finish Line - S3-E23

Trivia: In ARGUS one of the prisoners is Cheetah, she is an enemy of Wonder Woman.

Finish Line - S3-E23

Trivia: Cisco refers to Savitar as being like Two Face, another DC super villain.

Luck Be a Lady - S4-E3

Trivia: Wally says he's going to move to Blue Valley. In the comics, Blue Valley is where Wally West (son of Rudy and Mary West) was from.

Invasion! - S3-E8

Trivia: The facility where the bunch of heroes are training is identical to the hall of justice from the 80's cartoon.

The Race of His Life - S2-E23

Trivia: The way the other Flash dies and vanishes is exactly how Flash did in the "Crisis on Infinite Earths" DC comic book.