Hidden within YouTube's mashup of 2013's most viral moments are even more original videos from this year's biggest sensations.
Portal A, the creative studio that helped produce the mashup "YouTube Rewind: What Does 2013 Say?", used YouTube's annotations feature to hide extended footage within the video. That footage can be uncovered by gliding your cursor over the main video, and clicking on the boxes that appear at anytime. Each box leads to a new unlisted video.
"What Does 2013 Say?" has accumulated more than 64 million views since being posted on Dec. 11. We've gathered all of the Easter Eggs in the video gallery, below.
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