Kitten and his box.
Official video. 2006 One of the earliest viral videos on youtube to feature kitten's in boxes.
Update: See the re-uploaded video in it's original quality here! • Kitten and His Box : Classic Viral Video
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Jon Stewart of the daily show featured it in his segment, "Health Care or Kittens Decision"
(You can watch it here: https://www.cc.com/video/3ubhy4/the-d...)
Since then these kitties have been featured in numerous television ads, such as Fresh Step Cat Litter Commercials, and a whole host of television shows.