In the scene where Will is walking to class and a girl yells "wanker" at him, the actress was not asked to say this. The extras were told to intimidate Simon Bird and she improvised the line.
Jay's fake ID has the name "Bret Clement". This is an amalgam of The Flight of the Conchords Bret McKenzie and Jemaine Clement
Jay has an Australian driving licence which he is going to use as his fake ID. The address on it actually exists, located about 60 miles SW of Melbourne, Australia.
The fake ID that Jay uses in to get served in the Black Bull is a real Australian driver licence from Victoria, and the address is real too.