Continuity mistake: In a deleted scene (available on the DVD) between Will and Marcus in Will's flat, we get to both see and hear clips of Countdown on Will's TV set. The errors are with the utilisation of Countdown for this sequence: The way it's laid out it doesn't just work like that on the Countdown programme itself. On the deleted scene in question, the countdown clip starts with the theme, when we next see it on Will's TV it's on a word game with the clock music running, then a couple of minutes later we hear that the clock music has started again but there's been no new selection of letters or numbers. When Marcus sits back down again at the end of the scene the starting theme tune for Countdown begins again.
Continuity mistake: During the hospital scene, after Suzie asks, "That right Will?", we see behind him in the background, a lady with a green skirt, presumably a nurse, but then when Will says, "So your mum's gonna be okay", we now see two men in green where the nurse was, then cuts to Marcus, then to Will again, but now we see the lady again. After that Suzie arrives and the men in green are back.
Plot hole: When Hugh is walking near the park gate, he should have seen Marcus. Marcus was on the same side of the post as Will was.
Audio problem: When Marcus is opening the CD on Christmas you can hear the rip of the wrapping paper just before he actually rips it.
Continuity mistake: When Suzie, Will and Marcus are at the hospital, while Suzie handles the glass of water to Marcus, we see a man with a beige jacket passing behind them. Then the nurse arrives asking them if they're with Fiona Brewer, and we see the same man passing again.
Continuity mistake: When Marcus' mom is crying and getting his breakfast ready, Marcus asks if he should get his own breakfast, and his mom says "No, I'm doing it." While she says this, she's opening the box of cereal, but then it shows her pouring and spilling the carton of milk, with cereal already in the bowl. (00:11:00)
Continuity mistake: When Marcus is in the class doing maths, when the shot faces the professor Marcus is at the back playing with the cube thing, but when it faces Marcus he is sitting back thinking of a way to make his mum happy.
Continuity mistake: When Will takes Fiona and Marcus to have lunch, the cars in the background keep changing throughout the scene.
Continuity mistake: When Marcus and Will are playing pool, there are a couple of shots of Marcus and there are a few balls on the table in front of him. However, a few shots later, there are more balls and they have all completely changed position even though they both haven't taken a shot or touched the table.
Continuity mistake: In the last scene where Hugh's character and the two boys are sitting on the couch, Hugh gets up to go to the kitchen, taking his remote with him. In the next shot of just the boys the remote is lying on the table in front of where Hugh's character had been sitting. In the next shot when Hugh is coming back he's carrying the remote back with him.
Continuity mistake: When Will is at Marcus' house celebrating Christmas, it's not only the discman box that changes. The box is placed next to the tambourine, but when Fiona stands up to receive Suzie, the tambourine is on the CD player box, and we haven't seen anybody touch it.
Continuity mistake: When Marcus and his mom are talking about the suicide note, a part in Marcus's hair changes from shot to shot. (00:28:15)
Continuity mistake: After Fiona is told that Marcus has been going around to Will's place she goes and interrupts Will's date at a restaurant. She later sits down to talk to Will and there is a side angle of her and a frontal angle. In one of the angles her necklaces are outside her shirt, in the other angle, they're tucked into her shirt. (00:49:25)
Continuity mistake: When Will sees the poster for SPAT on the wall it is a light pink, but when we see a close up of it it's white. (00:13:15)
Continuity mistake: When Fiona is in hospital and Marcus is at home, just before he finds the suicide note he is arranging some flowers in a vase. The shot then switches to the note, then when you see the flowers again they are in a different arrangement. (00:25:55)