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.
Continuity mistake: In the Season 1 episode "Bollo", Bob Fossil records Howard saying "Gorilla" on his talk box, which Howard does with a downward inflection at the end of the word. However, every time Fossil plays back Howard's "Gorilla", it has an upwards inflection at the end of the word.
Continuity mistake: During "Brand New Day", at one point, Dr. Horrible stabs a picture of Captain Hammer attached to a dartboard with a handful of darts, all right in the center of the picture. A few shots later as Dr. Horrible sits, suddenly the darts are far-more spread out. (It's in the background and can be hard to see, but it's noticeable.)
Continuity mistake: After Ton bashes Retsuko for not getting her tea right, she sings some death metal in the bathroom before joining Fenneko back at the computers and they start talking. Between them is a pink cup with some orange scissors, and an assortment of writing utensils. They are fanned out, but show that the red one is closed to Retsuko with the black in the middle and the yellow closer to Fenneko. When the camera changes angles to show them both sitting there, this order of pens is flipped, with the scissors still being in the same spot.Quantom X