Old Slappy is a large thresher that appears in The Highlands - Outwash.
In Borderlands: The Pre-Sequel, Sir Hammerlock ordered Jack's Vault Hunters to send two threshers to Pandora. One of them was Old Slappy (he emphasizes on their tendencies to "slap"). Later on, he had an unfortunate encounter with Slappy, who ate his right arm and left leg.
Hammerlock 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 is killed afterwards.
- Main article: Slap-Happy
- Old Slappy has an increased chance of dropping the legendary Striker shotgun.
- Old Slappy takes more damage when its tentacles are destroyed, although these will regrow soon after. Hammerlock mentions this during the fight.