Continuity mistake: The explanation that Cisco draws about the endless cycle changes in between shots, not counting the added words "past", present", and "future" (which he could have written when off camera, not that it would make sense to do so since he already explained what was past, present, and future). Where the loop crosses itself is higher up as well as the "FF + TR" being different.
The Flash (2014)
1 continuity mistake in Cause and Effect
Starring: Danielle Panabaker, Tom Cavanagh, Candice Patton, Grant Gustin, Rick Cosnett
Continuity mistake: In episode 2.09 of related show "Arrow," during the day the particle accelerator is activated, Barry spends his time with Oliver, Felicity, and Diggle in Starling City. He arrives back in Central City just in time to see the particle accelerator activated, and he is in his lab because he was too late and missed the line at S.T.A.R. Labs. In episode 101 of "The Flash," Barry was never in Starling City during the day the particle accelerator was activated, and he and Iris actually attended the event. (00:02:10 - 00:11:30)
Harrison Wells: You know what? In battle, choose your weapon wisely. Some people choose a gun. I choose a Philips head screwdriver.
Cisco: Oh, oh. I'm sorry. You're so particular.
Harrison Wells: Ramone, could you just please? Have you ever worked with a tool before?
Cisco: I'm working with one now.
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.
King Shark vs. Gorilla Grodd - S5-E15
Question: Since David Hayter voiced King Shark, why not have him portray him in his human form of Shay Lamden?