The expression “no small feat” is used to point out a big accomplishment. The expression “no small feet” is used to point out big feet.

feat: (noun) accomplishment, bold act, heroic deed feet: (noun) (plural of foot) the lower extremities of legs-human, animal, clothing, or furniture; a unit of measurement
The expression “no small feat” is used to point out a big accomplishment. The expression “no small feet” is used to point out big feet.