As his name suggests, Elder Kettle is a browish-grey, anthropomorphic tea kettle with a spout nose and a chip-like mustache. He wears brown-grey shoes and white gloves. He carries around a brown cane.
Elder Kettle is a typical elderly sage, having a strong amount of helpful wisdom that allows the brothers to make the right, moral decisions in life.
A statue of him can be seen in the run & gun level "Rugged Ridge", suggesting that Elder Kettle (or perhaps an ancestor of his) may have been a knight or perhaps a philosopher.
The Elder Kettle is the first character Cuphead and Mugman meet after the introduction. He is well aware of the problem the brothers have gotten themselves into, and although disappointed at first, he decides to help them with their quest to gather the signatures of the Inkwell Isle resident's soul contracts. He gives the brothers a magic potion that allows them to fire a standard, rapid-fire projectile known as the "Peashooter" whilst warning them that their "friends" will not be so willing to sign their soul contracts. He also recommends that the brothers use the tutorial scroll he wrote to help them prepare for the battles they soon encounter.
After the brothers gather all the contracts from Inkwell Isle 1, the Elder Kettle will stop the brothers before they continue into Inkwell Isle 2. He will tell them that as they continue to gather strength by defeating the debtors, they will soon be able to stand a chance against King Dice and eventually the Devil himself. He also advises them that when the time comes, they must "do the right thing".
Should the brothers refuse to give the Devil the soul contracts and defeat him, Elder Kettle can be seen in the crowd with the former bosses, obviously proud that Cuphead and Mugman defeated the Devil and freed everyone from their soul contracts.