The album cover artwork from The Police's 1981 album Ghost in the Machine can be seen painted on a wall in 'The Firefly'. This foreshadows 'Reciprocity' where The Machine seemingly turns on for no reason.
A blue recycle bin in 'Reciprocity' in the alleyway where Peter kills a fleeing shapeshifter is labeled with a "Powder Blue" sticker, foreshadowing the blue powder bioweapon used in 'Concentrate and Ask Again'.
FRINGE DIVISION CASE FILE #311-12811
FRINGE EVENT: Shapeshifters being systematically executed
CLASSIFIED CASE CONNECTION(S): Shapeshifters
AGENTS ASSIGNED: Dunham
SUPERVISING AGENT: Broyles
FILE ARCHIVED BY: Grant Pollard, Lee Varner
WITNESSES/CONTACTS: Lieutenant Pike, Dr. Grant
LOCATION: Revere, MA
VICTIM(S): Dr. James Falcon, Jackie Bermudez, Zach Alpert
CASE REPORT SUMMARY:The Machine was built on Liberty Island, but no one was able to activate it. A dozen different power sources were tried, along with multiple diagnostics, but it remained unresponsive. NASA, the CIA, the NIH, and the government's top people had no idea how to operate it. Peter Bishop turned out to be the key when his mere presence created an electromagnetic spike that triggered the Machine.