This is “Unknown Karaoke”, a segment in which the guys try to sing along to a song they have little to no clue how the actual lyrics go. Things we learn from this bit:

• The words “vanilla” and “white” have now been replaced with “Andrew”
  (e.g. “Andrew bean ice cream is delicious”, “She just got her teeth Andrewed”)
• It’s no mistake that Will only knows the most creepy, murdery, stalkery parts of songs.
• Cumtard does the “meow” thing because when goes for the high notes, it sounds like someone stepped on a cat.
• Tully feels like a natural woman.
• Ellis just out Whammied Wham.