From Zelda Legends Wiki
Cue Ball was a sub-boss in Link's Awakening that Link could defeat by hitting it from behind with his sword. It ran around a central barrier and could only be hit by double-backing, because its head was invincible. Cue Ball appeared in the Angler's Tunnel (Level 4), and Turtle Rock (Level 8).
It is interesting to note his physical appearence is much like the A Link to the Past boss Arrghus and the way to defeat him is similar to the Ocarina of Time sub-boss Big Octo.