Gerald, better known by his nickname "Gator", is a large tank engine who resembles an alligator.
Although Gator's real name is Gerald, he is known as Gator due to his resemblance to an alligator. He longs to travel and is excited about going to sea. He works on a railway in a faraway land, which runs up into the high mountains and into a village. Once, Gator had to cross the bridge leading into the village, but became scared because of the bridge's massive height. In the end, Gator decided that he must be brave and crossed over the bridge safely.
Gator once visited Sodor. He was pulling a train and because it was foggy, Percy, who saw Gator, mistook him for a monster. Percy ran back toward the docks, scaring everyone else there into thinking Gator was a monster. After he introduced himself, he explained that he was not going to stay on Sodor; he was waiting for a ship. He told Percy all about being brave, making good friends with him.
Gator ended up missing his ship, so to pass the time, he was asked to collect a train from Duck's Branch Line and bring it back to the docks after Oliver, who was pulling it, broke down. His lamp was broken and he could not see, concerning Toad the brake van. During his journey, he met James at a junction. James, who did not know Gator yet, was frightened and puffed away as fast as he could, resulting in him derailing into a pond. When Gator nearly crashed due to being nearly blind in the dark, Toad decided to loan him one of his own lamps, and thanks to this spare lamp, they arrived at the docks on time.
Two nights later, Gator was heading to the docks to catch his ship and was surprised to see Percy being loaded onto the ship too. Percy explained that he wanted to work with Gator and run away from his fears, which Gator did not think would have been brave, leaving Percy to reconsider his decision. As the ship left, Thomasrushed into the docks, urging Cranky to stop the ship, under the impression that Percy was on-board. Cranky stopped the ship, but he was nearly pulled off the docks, forcing the ship to turn around. To Thomas' shock, Percy was not in fact on the ship. Due to the mishap, the ship was delayed yet again. The next day, Gator was finally able to leave after bidding an emotional farewell to Percy. As the ship sailed away, the two engines knew they had each made a good friend, knowing they may never see each other again.
For a long time afterwards, Percy was still sad about Gator leaving and kept thinking about him. He was told to throw himself into his work in order to drive Gator out of his mind. When some trucks ran away from Percy and got lost in a mine, Percy remembered Gator's advice about being brave. Percy was able to rescue the trucks and realised that thinking about Gator can also make him feel happy.
Gator came back to Sodor for Christmas, but there was a shipment of rock salt that needed to be delivered and the dock manager did not know where it needed to go, as the writing on his paper was smudged up. Gator was asked to go all around Sodor in search of the place where the rock salt needed to be delivered. Along the way, he wanted to greet Percy, but he did not seem to find him, thinking he had forgotten all about him. However, Gator finally met Percy, but was covered in rock salt after Percy bumped the trucks.
Gator is incredibly brave and longs to travel, while retaining a calm, grounded personality. He longs to travel out at sea, and works up in the high mountains, but also has a slight fear of heights.
Gator is based on a Colombian Steam Motor locomotive built by Sentinel Waggon Works Ltd. All four of these locomotives have been scrapped. Gator has been re-gauged from metre gauge to standard gauge.
Gator is painted two-tone green with gold lining and a red stripe, running board and bufferbeams. He has a brass nameplate on each side of his bunker.