If you watch Springwatch, the BBC's flagship nature programme and uniquely British badger-bothering tweefest, you may have witnessed this last night.
Not everyone was impressed, especially people who were eating their dinner.
This is all to do with "Spineless Simon", a stickleback fish who's featured throughout this series of Springwatch, which was filmed at RSPB Minsmere in Suffolk.
The fish was happily fanning away (this is what sticklebacks do apparently).
Then he spotted something in the silt and thought "I'm having that". But unfortunately that thing was a leech, which attacted itself to his EYEBALL with its ANAL SUCKER.
As presenter Chris Packham explained: "We think what was happening there, the leech was protecting itself when Si [the fish] attacked it. It attached itself to its eye using its anal sucker.
"We've got a close-up here – that's what you pay your licence fee for, folks."