Visible crew/equipment: During "Valerie", as Santana resumes singing right after Mike has somersaulted over Brittany, you can see a cameraman filming the girls' group in the bottom left corner of the screen. (00:32:15)
Continuity mistake: During Season 2, Episode 9 (Special Education), just as Blaine is singing "Hey soul sister, I don't wanna miss." for the last time, he is several feet in front of the other Warblers. But during the next shot, as he is singing ".a single thing you do.", he's right in front of them. So he jumped back several feet between two shots.
Answer: According to IMDb.com, Ian Brennan, one of the "Glee" writers and producers, is listed as the uncredited narrator voice.
Michael Albert