Spartacus is first visible playing in Ryan's room before he pops up in a jump scare, however following during his monologue cut short by his mother attempting to enter his room Batman: Arkham Origins is seen in the midst of a cut-scene with no transition between the show and game.
When the Police Officer is searching Pfeifer's house and turns sideways while going around the first corner, we can see he has no ammo magazines in the ammo pouch on his Sam Browne duty-belt. No Police Officer would ever go out on patrol or answer a call like this without extra ammo in this pouch.
In real life at Beatrice High school in Nebraska, their colors are Orange and Black and the high school's mascot is the Orangeman.
If you look closely whenever he is visible, Charlie wears black hockey gloves on his hands.
During Reese's death scene in the climax of the film, pay close attention to the wooden scaffold, multiple shadows appear. It's reasonable that one of these shadows is Charlie, however (being multiple shadows) it is most likely that these shadows are the production crew appearing as the result of the spotlight shining on the characters in this scene.
At the end it is revealed that Pfeifer is Alexis and Charlie's daughter. She is a senior in high school Charlie died 20 years before so she would of have to been conceived before he died for her to be his daughter. Therefore Pfeifer was a 19 year old senior. She was born almost 7 months after her father died. Her mother made sure to hold her back to stay with Reese and exact their revenge.
Reese calls Pfeifer "Cassy" and "Cassidy" several times when they are alone towards the end, usually when they are running or panicking.