The part where Nick shoots the helium balloons to release the helium to change the pitch of the Link's voice wouldn't work. Helium which is lighter than air would just float up to the rafters and escape out of any crack in the ceiling.
The amount of blood on the little girl's knee changes between shots.
This was one of the few episodes where the captain shows a sign of vulnerability, when he is singing along to "I Will Survive.
The Twins: The lie/truth behavior of Barbi and Staci, the twin scavenger 'links, is that of a classical logic puzzle (often presented as twins at life-or-death doors, or guards at a fork in the road leading to two life-or-death villages), and seen in many stories, including the movie Labyrinth (1986), Kate's solution is the correct one.
Trivia: Dragon's teeth are one of the few things that can kill Carl.
The "statues" in the Gorgon's loft move noticeably, showing that the director simply painted guys white rather then get real statues.
Noticed the use of 2 different cars as the squad car. One is a Chrysler Concorde and the other is a Chrysler LHS. Not the first Goof. Watch the grill on cars used and you'll see the difference sometimes. Started to notice in episode before this one, but watching this one and following ones confirmed the use of two different cars.
While Jesse James' final burial place is in some dispute, he's never been placed in Joliet in Chicago.
Al Capone is buried at Mt. Olivet in Chicago, not the Joliet Annex.
Al Capone is referred to repeatedly as a "serial killer," but he doesn't qualify by any reasonable standard.
Captain Page: ... and you can point that out at the next Special Unit national convention.
The captain reveals that links exist in other cities (previously, it had been implied that links all gravitated to Chicago), and that there is an SU2-like unit in NYC (and probably elsewhere) as well.
When Nick is holding the pipe and the gargoyle reaches out and bends it one-handed, that should have only worked if Nick were also that strong to hold onto it.
When Sean is explaining about why gargoyles festoon European churches, the 'unexplained disappearances' graphic behind him changes before he points the remote at the display to begin what looks like a Powerpoint presentation about churches and pictures of missing people.
Trivia: The convenience store clerk will be seen again as a motel manager in "the Skin".
Trivia: When Carl and Nick are fighting, Carl always gets in the last punch.