Sewaddle sleeping by covering its head with its hood
Sewaddle is a caterpillar-like Pokémon with a broad, bitten leaf enfolding its head like a hood. Its large, spherical head is an orange-yellow with two small, close-together knobs on its forehead. Sewaddle's eyes are black and circular, and its mouth has a downward-pointing, crescent-shaped orange snout with a sharp tiny tooth at either end. The underside between the snout and its neck is white. Its green body has three segments with a pair of stubby, spherical orange legs on each segment.
Sewaddle makes itself leafy clothes using chewed-up leaves and a thread-like substance it produces from its mouth, though Leavanny tends to make its first set after hatching. By folding it over its face, its leafy hood is used to help hide it from enemies, whether awake or asleep. It has been shown to eat berries, but when food is scarce it will eat its leafy clothing as an alternative.
Sewaddle appears to be based on the caterpillar form of the silver-spotted skipper, which produce silk and fold leaves over themselves for shelter. It also shares some characteristics with the larva of weaver ants, which produce silk used to form nests. It may also take inspiration from walking leaves. The large leaf around its head could represent a baby's bonnet.
Sewaddle may be a combination of sew and waddle (referring to how a baby walks) or swaddle (to wrap a baby in cloth).
Kurumiru may be derived from 包む kurumu (to wrap up), 胡桃 kurumi (walnut tree), or お包み okurumi (swaddle).