The phrase is a notorious internet creepypasta and "lost media" legend. While it sounds like a cute animal video, it is actually a fictional horror story about a supposedly cursed or disturbing file. Summary of the Legend

This specific story is a great example of . It plays on the "uncanny valley" effect—taking something universally seen as innocent (kittens) and associating it with something hidden and or dangerous.

: A user finds a file titled Kittens 13.mp4 on an old hard drive, a shady forum, or a file-sharing site.