This episode is one of many that Julien has been kidnapped and Fred's first time. Julien's first kidnapping was in "Dr. Blowhole's Revenge", his second in "The Falcon and the Snowjob" when a hungry male falcon caught him. Like in his first experience, Julien manages to botch the villain's plan this time around.
The Red Squirrel complains that "everyone gets underlings except me."
The very same metal wall with the arm and ankle cuffs that appeared in Dr. Blowhole's lair is also used in the Red Squirrel's base. Though the cuffs were too big to hold Mort. If he'd been smart enough to realize this, he could've jumped off the wall.
It is revealed in this episode that in Central Park, acorns are considered currency, similar to human money (except human dollars don't grow off of trees while acorns do as Private pointed out).
This episode takes place in the park for most of the episode.