Impossibru is a single frozen shot of Ayumu Kato with his mouth stretched wide and eyes squinted in a look of pure disbelief, captioned with the mock-Engrish spelling of 'impossible'1. The 'ru' ending mimics how the loanword インポシブル (imposhiburu) sounds when transliterated back from Japanese, which is the whole joke posters lean on when slapping the word under the still3.

People use the image as a reaction to anything that reads as absurd, unfair, or physically improbable, from bad news stories to game glitches2. It sits in the same 4chan-era family as Rape Face and other 'panic face' macros, where the humor comes from a real facial expression pushed to a cartoon extreme3. Some edits swap the caption for other broken-English exclamations or paste the head onto other bodies, but the plain white-Impact-caption version is the one that stuck4.

The common convention is to drop the unmodified Kato still into a thread as a reply to a claim, event or image that feels ridiculous, with 'impossibru' typically set in white Impact caps across the bottom. People often omit the caption entirely once the face is recognizable enough on its own, or swap in a different mock-Engrish word for a specific in-joke.