He is a large, fat tan lizard-resembling alien with a pair of horns (one of which a gold ring hangs from) and a pair of antennae protruding from his head, and he sprouts a tail that is as thick as his fat legs. During the voyage, the ship encounters a supernova. Jim (while securing lifelines of all pirates) saves Silver from falling just in time. The supernova then devolves into a black hole, where Arrow falls. The burst of shock waves and maximum engine power enable Amelia to pilot the ship to safety. Amelia mourns the loss of Arrow, and suspects Jim of failing to secure the lifelines, while Arrow's line was actually cut by Scroop. As one of the pirates in John Silver's crew, Grewnge seems to be the cannon's expert, which is demonstrated when he fires with great accuracy at several incoming asteroids during the destructive meteor shower as well as the longboat Jim Hawkins, Captain Amelia, and Dr. Delbert Doppler were escaping in during the pirates' siege on the Legacy. Meanwhile, Grewnge and the pirates corner the group here; using a back door, Jim, B.E.N., and Morph return to the ship in an attempt to recover the map. He is later provoked easily to any opprobrious insult regarding his weight, as he rears in to kill Doppler for doing so, but this distraction leads to his arrest alongside the remaining crew. Despite his arrest, Grewnge is last seen cheering along with the crew for Jim for saving them from the exploding planet.
Yeah, baby. Ba-boom!
That's it! Come to papa!
I pummel you good!
"Yeah, baby. Ba-boom!"
"We are wanting to move."
Silver and his crew about to get in
Grewnge about to fire
Turnbuckle, Crex, Mertock, Grewnge, and Blinko sleeping with Silver
Turnbuckle and Grewnge restraining Jim
Grewnge yelling after being bitten by Morph
"I pummel you good!"
Dr. Doppler getting the upper hand
Grewnge's defeat along with the other surviving pirates