The 'Why the tip of the penis is mushroom shaped' meme is based on a legitimate evolutionary psychology theory known as the semen displacement hypothesis. The theory posits that the human glans evolved its unique shape to physically remove the semen of other males from the reproductive tract, ensuring one's own paternity. On the internet, this startling biological fact became a viral sensation, often formatted as an educational infographic. It is widely used to humorously explain aggressive competitiveness or to shock social media users with unexpected 'fun facts' that are technically true but socially awkward to discuss.