It’s the Trending Now Top 5 Countdown for December 5, 2012 – where we gather the hottest and most outrageous must-see YouTube videos hitting the web today and send them all straight to your screen. It’s like watching the best of YouTube — only faster!

From Jimmy Fallon, Mariah Carey, and The Roots performing “All I Want for Christmas is You” to Jay-Z’s conversation with an old lady on the subway, we have you covered right here on What’s Trending.

#5: Jay-Z Rides the Subway, Adorably Explains Who He Is

#4: Mr. Burns Explains the Fiscal Cliff

#3: Jimmy Fallon, Mariah Carey & The Roots – “All I Want for Christmas is You” with Classroom Instruments

#2: Neil Patrick Harris & Nathan Fillion in “Doctor’s Office” (Neil’s Puppet Dreams)

#1: Spartan High School Style

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