Continuity mistake: Hanna and Alison are at Hanna's home, when the bell rings. Hanna takes a look through the window directly next to the door, and claims it's just Travis. When she opens the door and goes outside, there is no window visible. At least not any kind that could have seen Travis. It seemed to just have disappeared mysteriously. The transition of shots between the set of hanna's interior and exterior is done very poorly. (00:12:10)
Revealing mistake: When the police ring Ashley's phone, we catch a glimpse of the screen as she answers it. The phone is not in call mode.
No One Here Can Love or Understand Me - S5-E11
Continuity mistake: In the beginning of the show, when Emily and Spencer are at the brew, they are seen holding a blue mug filled all the way with whipped cream. Pay attention to Spencer's mug; the amount of whipped cream changes between shots.
Through a Glass, Darkly - S5-E14
Revealing mistake: When Jason shows Ali the family photo you can see that Jason and Ali have been badly, almost cartoonily photoshopped in.
Continuity mistake: When Hanna and her mum are in the kitchen talking about Hanna's dad and the beauty pageant, Hanna's phone keeps flipping over on the kitchen counter throughout the scene.
Character mistake: When Aria is taking her Maths Algebra test, we get a short glimpse of her paper at the start of the scene. Question 4 spells the word 'population' as 'popopulation' the second time it is written in the question.
Pretty Isn't the Point - S5-E20
Continuity mistake: The pizza slice that Hannah is eating when her mum starts talking to her and Emily in the kitchen jumps back onto her plate between shots. Her arms are also suddenly folded.
Bloody Hell - S5-E21
Continuity mistake: When Hannah is in her kitchen talking to her mum about Ted, one of the daffodils in the vase that Hannah's mum was preparing is suddenly no longer in its original position after Hannah takes a bite out of her apple.
To Plea or Not to Plea - S5-E22
Revealing mistake: When Emily calls Varjak's number from the Tony's Pizza receipt, her phone says that it has no service - meaning she should not be capable of making any calls.
The Melody Lingers On - S5-E23
Continuity mistake: When Ashley and Ted are in the kitchen talking about Allison's trial, Ashley's hands go from raised to down by her sides and back again between shots when she says "It's not a way to start a life together."
The Melody Lingers On - S5-E23
Revealing mistake: When Aria calls Spencer after the first trial scene, Spencer's phone is not in call mode.