Deliberate mistake: In season 4 episode 7, 'Brian the Bachelor'. Cleveland is sitting in a chair in a waiting room and is getting really nervous. Peter tries to help him by tying him to a chair and when that doesn't work, he takes off all of their clothes. Peter ties Cleveland's hands to the arms of the chair and then takes Cleveland's clothes off. He couldn't have taken the shirt off while Cleveland's hands were tied to something without untying him or ripping the shirt, which he didn't do.
Deliberate mistake: When Stewie demands his device, he says, "Like a box of active grenades," and she gives it back. The pins weren't pulled, yet he runs and it explodes. (00:18:00)
Yug Ylimaf - S11-E4
Deliberate mistake: The time machine reverting causes everything in life to go backwards. However, although the characters' acts are reversed, their lines always sound normal. (00:08:00)
Chosen answer: It's a real song called "Elvira". Originally by Dallas Fraizer in '66, however, this version seems to be the Oak Ridge Boys cover version. However, the mega lesbians skip the verse and just sing the chorus after the opening line.
Bishop73