Mlem is widely used online as a written joke for the tiny licking or tongue-out motion often seen in pet photos and videos. The term became common in meme culture through animal posts and reaction edits rather than one single confirmed source clip. It stuck because the word itself sounds like the action people are describing. Today, the sound is still used in short-form videos, pet compilations, and cute reaction memes where a fast, soft joke lands better than a loud effect.