Teemo ranks #3339 with 25 male pet uses, and its origin is unambiguous: Teemo is a champion in League of Legends, Riot Games' massively popular multiplayer battle arena game, released in 2009 and still among the most-played games in the world. He is a tiny, cheerful, deceptively lethal yordle who places invisible mushroom traps across the map. He is beloved and widely feared.
Why Teemo specifically
Among the dozens of League of Legends champions with distinctive names, Teemo has achieved a particular cultural prominence that makes it disproportionately likely to transfer to pets. His small size, round appearance, and the gap between his cute aesthetic and his annoying mechanical impact make him ideal for the same incongruity humor that drives names like Reginald and Sigmund. A tiny, fluffy dog named Teemo who has just destroyed a pillow is fulfilling the name's promise exactly. Teemo is gaming culture's contribution to the long tradition of naming small animals after things that punch above their weight.
Gaming names as a pet naming category
Teemo belongs to a growing category of pet names drawn from video game characters: Link, Zelda, Kirby, Pikachu, and Pichu are all part of the same pattern. What distinguishes the gaming category from movie or TV names is the specificity of the community: these names function as signals, immediately legible to other players and opaque to everyone else. Naming your pet Teemo is a way of marking yourself as belonging to a particular cultural world. It shows up on Pembroke Welsh Corgi owners and on small mixed breeds with pointy ears that physically recall the character's appearance.
The owners and the in-group signal
Teemo owners are almost certainly active or former League of Legends players, or close to someone who is. The name creates an immediate connection with other players who recognize it — "oh, is he annoying?" is apparently a common response at dog parks — and a pleasant blankness for everyone else. If you're considering this gaming-name register, Kaiju operates similarly as an in-group signal for a different media tradition.