Cosmo and Wanda went to the same high school together.
Apparently a lot of the students from Cosmo and Wanda's high school had lied about something personal and that they've been hiding the truth up until now. (For example, Luthor Lex claimed to the school he still does football but he reveals at the end that he now does ballet)
Timmy claims in this episode that his family has bladders of steel.
Lex Luthor - Luthor Lex's name is a spoof on Superman's enemy.
Timmy having to hold it despite needing to go to the bathroom.
Britney Britney saying random things.
Although this episode premiered in 2005, it was produced in 2003 according to the credits.
It is said that there are no doors in Fairy World, yet doors have been seen and used by fairies all the time in episodes before and after this one (ex. the doors at the Pointy Crown in This Is Your Wish).
Cosmo said that he invented oxygen and that every time the fairies inhaled they had to pay him a quarter. However, it was said in Transparents! that fairies don't need to breathe.
When Luthor offered his job resumé to Cosmo, his name on the resumé said Luther Lex rather than Luthor Lex.