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. Later on, he had an unfortunate encounter with Old Slappy, who ate his right arm and right leg.
Vengeful at Old Slappy for the loss of his limbs, Hammerlock enlists the Vault Hunters to kill it, providing his prosthetic arm as bait to lure it out. Old Slappy emerges from the extraction plant lake intent on consuming his next meal, but is killed afterwards.
- Main article: Slap-Happy
- Old Slappy has an increased chance of dropping the legendary Striker shotgun.
- Like most threshers, Old Slappy takes more damage when its tentacles are destroyed, though they regrow over time. Hammerlock mentions this during the fight.
- Like Terramorphous the Invincible, Old Slappy has two separate models.
- When it initially surfaces from the reservoir, Old Slappy will perform a taunt. Being a passive model in this case, Old Slappy does not attack, nor could it be harmed or draw fire from nearby Hyperion units.
- After the taunt animation has ended, Old Slappy properly reveals itself and can be fought normally.