From Monkey Island wiki
Gunner Simkins is the sole known lackey of Admiral Casaba in Escape from Monkey Island. Casaba is hired by Ozzie Mandrill to guard the waters between Jambalaya Island and Knuttin Atoll to prevent any pirates from Knuttin from reaching Jambalaya. Casaba is intensely paranoid and orders Simkins to fire "the really big cannon" at the first sight of pirates gathering on Knuttin in groups of more than two. Simkins is a very unwilling lackey, appealing to Casaba when he orders to fire upon Guybrush (who is pretending to talk with the puppets Little Guybrush and Little LeChuck) that "[his] ears are still ringing from the last time."
Simkins is heard but never seen as he presumably remains below deck to fire the really big cannon at Casaba's demand.
- Escape from Monkey Island (unseen but heard)