Shortly after Leonardo wakes up Casey remarks that he "sounds different". This is an inside joke to the fact that Seth Green had replaced Jason Biggs as Leo's voice actor.
This episode takes some elements from the first Teenage Mutant Ninja Turtles (1990) movie when they seek refuge in a house in the woods.
Leo's voice got deeper and more adult like in this episode and onward. It is explained in-show that this change of voice was caused by damage to his larynx following the aftermath of "The Invasion Part 2".