Mrrp is the short trilling noise cats naturally make as a greeting, and clips built around it spread widely on TikTok, YouTube Shorts and pet meme pages. Creators looped the repeated mrrp and meow pattern over close ups of house cats, turning a normal pet vocalisation into a recognisable reaction sound. It stays popular because almost anyone with a cat knows the noise, and because it works without context for cute, needy or talkative moments in short videos and streams.