RSSWhat's the deal with referring to copyright/trademarked material in a script?
Internet Filmmakers' FAQ
As with all remotely legal issues touched upon in the Internet Filmmaker's FAQ, this information should be used as a guide only. You should ALWAYS talk to a qualified entertainment lawyer regarding any legal issue.
Generally speaking, you can refer to trademarks by name without permission. The only exception would be using someone else's trademark in what amounts to a competitive product. For example, you couldn't have a superhero named "Spiderman" or a spaceship named "Enterprise" (both trademarks), although you could, for example, have a character look around a high-tech building and say, "What the hell is this, the Starship Enterprise?" or sarcastically say to someone hanging from the side of a building, "Who do you think you are, Spiderman?"
With regards to having a character sing a few lines from a copyrighted song, you will need obtain clearance to perform the said piece from your country's music clearance organisation (ASCAP, BMI, AMCOS etc). Depending on the profile of the music, this may or may not attract a fee. Generally if you are not using an original recording (i.e. having the character sing the lines instead of the original artist) clearance is a lot cheaper. Again, contact a lawyer.
A great place to start with many copyright clearance missions is the Copyright Clearance Center.