Revealing mistake: When Oliver is threatening Mathis' lawyer, he shoots him in the shoulder. When Oliver grabs the arrow and pushes it through the shoulder, there is a significant difference between the angles. Where the arrow is coming out, it is practically horizontal, but in the chest, it is at a thirty degree angle.
Arrow (2012)
1 revealing mistake in Crucible - chronological order
Starring: Katie Cassidy, David Ramsey, Stephen Amell, Colin Donnell, Emily Bett Rickards
The Magician - S3-E4
Revealing mistake: When Oliver meets Thea at the Grind and Jot Cafe (Which looks unsurprisingly like CC Jitters) you can see the cups on the table are from CC Jitters. (00:20:50)
Lone Gunmen - S1-E3
Oliver Queen: I'm having some trouble with my computer and they told me you were the person to come and see. I was at my coffeeshop surfing the web and I spilt a latte on it.
Felicity Smoak: Really?
Oliver Queen: Yeah.
Felicity Smoak: Because these look like bulletholes.
Oliver Queen: My coffeeshop is in a bad neighbourhood.
Trivia: Although Laurel is a couple of years older than Sara, Katie Cassidy is only about a month older than Caity Lotz.