Pingu is the wordless claymation penguin at the centre of the Swiss children's series of the same name, where his honking voice and expressive gestures carry most of the comedy. Short Pingu clips have long circulated online because they work without dialogue, and the knock knock moment fits that style perfectly. Shared by fans who call themselves Pingu lovers, it has found a second life as a 2026 meme sound for door reveals, surprise entrances and playful interruptions in short-form videos.