Tree House of Horror X - S11-E4
Continuity mistake: In "I Know What You Diddly-Iddly Did", just after Ned has been run over, he turns from a werewolf into his normal self. If you look carefully, his left ear turns brown for a second before turning yellow again.
Chosen answer: After only five minutes of researching this, I found two times when the iPod was spotted in the Simpsons. First, when Homer was in some sort of religious store, he saw a poster for iGod with a clear silhoute of God rocking with an iPod. That episode is titled "Thank God it's Doomsday". It's episode ID is GABF14, meaning it was from Season 16. In another episode, which takes place at Lisa's prom, the DJ is simply an iPod. This episode is "Future-Drama" and, believe it or not, aired just bfeore "Thank God it's Doomsday", meaning it too is season 16. Hope this helps.