I give you a group of three. One is sitting down, and will never get up. The second eats as much as is given to him, yet is always hungry. The third goes away and never returns.

Why this works

This riddle cleverly plays with the characteristics of a stove, fire, and smoke. The first clue, "one is sitting down, and will never get up," refers to the stove itself, which remains stationary and doesn't move. The second clue, "the second eats as much as is given to him, yet is always hungry," describes fire, which consumes fuel (like wood or gas) but is never satisfied and will keep burning as long as there is material to consume. Finally, "the third goes away and never returns" pertains to smoke, which rises and disperses into the air, often disappearing completely, thus never coming back. Each element distinctly fits the clues, showcasing a fun interplay between their functions and characteristics!