The site www.ancientmexicanwisdom.com is a real site owned by Warner Brothers.
Fred reveals to Alejo that the reason why Shaggy eats so much and doesn't gain any weight is because he has a high metabolism.
During a chase scene with the monster, the gang can be seen in front of a movie theater. The showing at the movie is "Legend of the Vampire". This is a nod to Scoubidou et les Vampires (2003), which came out a few months prior.
Instead of the correct reptillian (or canid) monster, a purple Bigfoot was used for the Chupacabras.