Joel Willans, from Finland, tweeted a photo of some kids’ competition entries during a Lego exhibit on Sunday 30 July.
Next to much larger creations - including a multi-level ship and what looked like a robot with legs - was 12-year-old Riley’s worm.
A single yellow Lego block.
“Riley, you’re a genius”, Willans tweeted.
In less than a day, the photo has had more than 70,000 retweets and 155,00 likes.
Twitter users replied with their astonishment at Riley’s “genius” creation - some even referring to him as a “conceptual artist”.