Then she and Blaine sing a duet, an original song called “Extraordinary Merry Christmas.” Or I assume it’s Blaine and Rachel, because I see their lips moving, but the auto-tune on their voices is so extreme it could have been me and Dennis singing. And their whole flirty thing makes my skin crawl, especially in an episode where Brittany and Santana do not exchange one single freaking word. What was it you said, Rachel? “All I want is what’s coming to me? All I want is my fair share”? Me, too."
— "Glee" Episode 309 Recap: No Box