Old Slappy is a large thresher that appears in The Highlands - Outwash.
Sir Hammerlock once had an unfortunate encounter with Old Slappy, which resulted in Hammerlock losing some of his limbs. He enlists the Vault Hunters to take his prosthetic arm as bait to lure out the behemoth and put the matter to rest violently. Old Slappy emerges from the extraction plant lake intent on consuming his next meal, and it's up to the Vault Hunters to finish the job, one way or another.
- Main article: Slap-Happy
- Old Slappy has an increased chance of dropping the Striker.
- Old Slappy takes more damage when its tentacles are destroyed, although these will regrow soon after.