YouTube's very own celebrities act out some of the cultural memes of the year in the video service's end of year "Rewind" video. These include Grace Helbig taking a selfie, the Smosh brothers and Fine brothers taking the Ice Bucket Challenge, Bethany Mota's rendition of "Let It Go" from "Frozen" and Freddie W taking over Conan O'Brien's late-night talk show. Other YouTubers give us their recreations of the year's biggest video hits -- like Pharrell Williams' "Happy" and Meghan Trainor's "All About That Bass." As we zip from continent to continent, via Minecraft bricks, devil babies and more, it's briliantly edited, riotous fun -- even if you don't know who all the stars are. For more on the video, read the story over at AdAge.com.