Dudolf's illustrated optical puzzles were the latest in a year full of fun optical illusions going viral online, but they didn't offer people the opportunity to argue about them so they weren't the big winners of the year.
However, there were some real gems posted well before Dudolf's doodles, like the cat walking up downstairs, the empty field that's actually full of sheep, and the radical "color changing hair!" illusion.
But not all the illusions that went viral were awesome. There was the dumb "guys does this say Greg or Corey", the dumber "which color matches the shoes the best?" and the ultimate in viral dumbness "what color is this dress?".