Mannaggia chi non crede is an Italian phrase that roughly means damn those who do not believe, and it circulates online as a short reaction clip rather than as a line tied to one widely documented film or show. Italian speakers recognise it instantly as an old-fashioned, theatrical curse of frustration, which is part of why it travels well in memes even for viewers who do not speak the language. Creators reuse it to punctuate disbelief, exaggerate a reaction, and give a short video a distinctly Italian comic flavour.