Going Rogue - S1-E4
Trivia: Kahndaq is mentioned heavily in this episode. Kahndaq is a fictional country, home to DC anti-hero, Black Adam.
Trivia: Tom Cavanagh, who plays Reverse-Flash after he assumes Dr. Wells' identity, and Matt Letscher, who plays Reverse-Flash/Eobard Thawne, played father and son on Eli Stone.
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.
Trivia: The woman that knows Oliver is Sandra Hawke, mother of Connor Hawke, the second Green Arrow.
The Man in the Yellow Suit - S1-E9
Trivia: Amanda Pays plays Dr. Tina McGee, head of Mercury Labs, a rival to S.T.A.R. Labs. She also played Tina McGee in the 1990 TV show The Flash, however in that series she's the one who helped Barry and built his special suit.
Fast Enough - S1-E23
Trivia: While Barry is running through the wormhole we can see Caitlin as Killer Frost, the Flash museum and the Legends of Tomorrow.
Fast Enough - S1-E23
Trivia: The metal hat that comes out from the wormhole belongs to Jay Garrick, aka the original comic book Flash.
The Man in the Yellow Suit - S1-E9
Trivia: The back pack that Iris gives to Barry has two references - the bag has the colors of the Flash in the comics, red and yellow, and inside there is a comic book of the space ghost, another super hero character.
Things You Can't Outrun - S1-E3
Trivia: As Barry is going up the stairs in the police station he says he doesn't want a museum dedicated to him. In the comics Flash has his own museum.
Tricksters - S1-E17
Trivia: When Jesse learns a new Trickster is copycatting him, he tells Barry and Joe that when he terrorized Central City, days without casualties were as rare as the Chicago Cubs winning the pennant. A few months after the episode aired, the Cubs made the playoffs, but lost the pennant in a four-game sweep; they won the pennant the following year and went on to win the World Series for the first time since 1908.
