Deliberate mistake: When Howard enters Figgins' password to hack into his AOL account, Figgins' inbox is obviously visible behind the login box, which simply disappears once the password has been entered. In addition, look closely at the inbox and you'll see that not only is there no mail, they are actually in GMail (the logo has simply been edited out of the top corner).
Glee (2009)
1 deliberate mistake in season 2
Factual error: In season two the show makes Dalton look like it's in a suburb of Lima. Dalton Academy is suppose to be located in Westerville, OH, which is two hours southeast of Lima. Kurt & Blaine would not be able to go to the "Lima Bean" coffee shop every day if this was the case.
Laryngitis - S1-E18
Sue Slyvester: See, that's the problem with your generation, you're obsessed with labels. So what if you like show tunes, it doesn't mean you're gay. It just means you're awful.
More trivia for Glee
Question: Who is the narrator for the previous episode montages?
Answer: According to IMDb.com, Ian Brennan, one of the "Glee" writers and producers, is listed as the uncredited narrator voice.
Michael Albert