Tis the season for a festive Instagram meme challenge. After Garcelle Beauvais reposted a meme of herself (from @themorganletters_) on Pharrell's shoulder, the "Elf On A Shelf" challenge was born and has since taken over the social media platform. Scroll on below to see the many ways in which Hollywood is celebrating the good ol' fashion viral cheer with similar reactions from the likes of Mariah Carey, Kerry Washington, Elizabeth Banks and more!