Jorgen Von Strangle was in cooking class when Timmy wished for him to be in the Wish Fixers building.
The Pixies were last seen as darts for Jorgen's dart board game in "Pixies Inc.". This episode however shows them free and no longer being used as darts. It is possible they were able to trick Jorgen into letting them go through good behavior.
Apparently HP and Sanderson consider microbiology more boring than they are.
Cosmo calls Timmy "CheeseBoy Squarepants", this is an obvious and (intentionally) poorly concealed parody of Spongebob Squarepants. Which means that Cosmo probably knows SpongeBob.
Sanderson: "Pay no attention to the fairy in the robot." - This quote is a reference to the film The Wizard of Oz. Cosmo and Wanda also say "pay no attention to the fairies opperating the fudgehead suit" in the Jimmy/Timmy Power Hour.
When Timmy wishes Cosmo and Wanda are made of rubber, the poof cloud says "Rubber Soul". Rubber Soul is a Beatles' album first released in December 1965.
Wanda's "Bad Wish" senses and "I don't trust on Pixies" senses are a parody of Spiderman's Spider Senses.
Head Pixie's line "Go me, go me, it's my birthday", is a parody of "Go, shawty, it's your birthday" which is the opening verse of 50 Cent's song In Da Club
A running gag in this episode is that Timmy makes a bad wish and after he signs the contract HP will turn up the device and shock Cosmo and Wanda.
Whenever HP points out to Timmy about something in the contract, he would say "Son of a gun", a very famous phrase.
How could the Pixies shock Cosmo and Wanda to death when fairy-type creatures are immortal (meaning they can't die)?