The mug shot of Edward lists his number as 208241138. If you assign the numbers to letters of the alphabet, you get 20=T, 8=H, and 24=X. THX-1138
The homework assignment on the blackboard is the same as Indiana Jones assigns in Raiders of the Lost Ark - Michaelson, chapters 4 and 5.
One of the technical drawings in the main character's notebook is the Tardis center console from the time travel themed series Doctor Who (1963).
The video game cartridge in the Atari time machine is Pitfall.
Kevin Ulrich's illustration and explanation of the Multiverse theory of time travel is a nod to Back to the Future Part II where Doc Brown provides a similar illustration and explanation to Marty McFly.