From Muppet Wiki

Louis is a French Canadian otter from Sesame Park. His name is pronounced "Louie," and he is best friends with Basil. Although Basil's constant questioning sometime annoys Louis, he tries to be patient and helps teach Basil French words. Louis was with Sesame Park for its entire run and was among the few characters to be consistently played by the same puppeteer. He also appeared in Basil Hears a Noise.