If you look in the background of the "I Wanna Be a Boy" song, when Spot/Scott is on his skateboard, you will see a billboard for the Barry Anger Show, which proves to be important to the plot later on.
The little girl voiced by Emma Steinkellner in the opening song first appeared in Teacher's Pet: Never Take Candy from a Kindergartner (2001), where she has a crush on Leonard and then moves onto Scott.
At one point Spot breaks out in song and is joined by other animals in a forest. In one shot the sound of a dolphin is heard, although none are present because, again, the scene takes place in a forest.