Ho Yay: Thistle clasps his hands, bats his eyes, and refers to the emperor as "my Cactus King."
Memetic Mutation: Modern viewers may recognize the mushroom dancers as the base for the Awesome Smiley.
Nightmare Fuel: The Cactus King threatens Thistle with an extremely excruciating death by the use of a giant shredding maching. Not to mention the suspense of him escaping at the very last second while the creepy guards slowly approach his cell to take him to the execution chamber.
At the end of the mushroom song, Michael Mushroom and the three dancers suddenly grow fangs.
From the sequel, Mrazomor himself. He has ice powers and has a jagged, sharp appearance, casually freezes his henchmen to death, plots to freeze the sun, has a deep and raspy voice...and succeeds in freezing/killing Thistle in the climax. Definitely scarier than the previous film's villain.
True Neutral: Baron Burr brought magic to the forest and gave Peter the power to speak animal, but gave Cactus King the prophecy and put a time limit on Peter's new talent.
Ugly Cute: Thistle is green, stringy-haired, pouch-eyed and buck-toothed, but his general niceness and put-upon–ness make him fairly endearing.
Uncanny Valley: Sunchica in the sequel may invoke this for some. Her coloring looks a lot more...painted, than the rest of the cast, her eyes tend to look lifeless due to it; overall she has a strange sort of artificial look. Possibly justified, since she's a fairy, but still, eesh.
Viewer Gender Confusion: A very short-lived example. Thistle looks like a girl until he takes his hat off and starts talking. (Actually, even his name sounds more suited for a girl than a guy.)