Lego is a toy brand name that has migrated into pet naming — almost always for dogs owned by households with children who had significant naming input, or by adults with strong nostalgic attachment to the building brick system. The name has a bright, blocky energy that works well on chunky or colorful-coated dogs.
The Toy Brand Pet Name
Brand names on pets are more common than people realize: Oreo, Doritos, Cheerio, Lego. These names usually come from kids who reached for the first appealing word in their environment, or from adults who enjoy the playful incongruity of a corporate name on a living creature. Lego the dog is implicitly a dog that someone in the household loves building things, loves color, and takes joy seriously. Corgis and other low, chunky breeds named Lego are a physical joke that works.
The Sound Case
Two syllables, soft L opening, ending in the bright open "oh" — Lego is easy to call and immediately recognizable. It doesn't have a natural nickname, which means the full name sticks in daily use. Compare Leo for a name with very similar sounds and much higher registry frequency that doesn't carry the brand association. Browse playful pet names for similar register options.
The Counter-Reading: Trademark Territory
LEGO Group technically owns the trademark on the name, which doesn't affect a pet license but does make the name feel like borrowed territory. The company also has the famous stance about the plural (it's LEGO bricks, not Legos), which your dog's vet will not care about. The name is lighthearted and it should be treated as such.