Radical
Old Dog

Mnemonic

A dog sits on the porch, gray around the muzzle, barely lifting its head as you walk by. Everyone in the neighborhood knows this old dog—he's been here longer than most of the families. This old dog doesn't need new tricks; he already knows them all.
Additional thoughts
Picture a wise, grizzled dog resting peacefully—the single radical 'dog' aged and weathered into 'old dog.' The simplicity reinforces that this kanji is just the dog radical in its veteran form.
Quick recall
A grizzled dog on the porch—everyone knows this old dog.