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.
Spongebob Squarepants - Cosmo calls Timmy "CheeseBoy Squarepants" This is an obvious and (intentionally) reference of the infamous character from the series.