The phrase you are referencing appears to be the title or a key plot point of a Japanese adult film or a specific genre of adult-oriented storytelling.
Sometimes, the "put it in her mouth" moment is a hilarious case of mistaken identity. Imagine a fancy cocktail party where a friend spots a bowl of what she thinks are gourmet chocolate truffles. She pops one in her mouth, only to realize—too late—that it’s actually a decorative ball of scented wax or a very strange-smelling goat cheese. A Female Friend Who Put it in Her Mouth Saying ...
When a female friend says something hurtful or unacceptable, it can have significant consequences, including: The phrase you are referencing appears to be
Here are the most common contexts that match your description: 1. The "Friends" Pilot Reference it can have significant consequences