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 - chronological order
Starring: Danielle Panabaker, Tom Cavanagh, Candice Patton, Grant Gustin, Rick Cosnett
Going Rogue - S1-E4
Continuity mistake: When Captain Cold shots Joe with the ice gun, he hits Flash instead, in the left side of his abs, but in the next shot the ice switches sides.
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?