Rebecca is a research vessel who explores everything about the ocean.
Rebecca is great at giving facts and information about the ocean and once advised Theodore to let Walter the whale return to his family. She is the leader of the "The Oceanic Institute" and works with Theodore, Northumberland, and Shelburne to find great things under the water. She has no trouble finding underwater treasures with her special sonar equipment. She and the salvage team once found an old ship's bell. Theodore looks up to her because she always does everything close to perfect. She also has a grumpy side, which she showed when Benjamin Bridge kept her up all night with his loud snoring. But even though she is not perfect, she is always fun to explore with and is the tugs' closest guide to the mysteries of the sea.
Rebecca had three different models in Seasons 1 and 2. In the early Season 1 episodes, she was completely faceless and nameless until she started out with a grey color, an all-white hull, and no eyebrows which was seen in the early Season 2 episodes (ex. Theodore in the Middle, Whale of a Tug, Theodore the Tug in Charge, Theodore Changes Sides and Foduck Stays Home). Later in Season 2, her eyes were bigger, her eyebrows were thick and grey, and half of her hull was painted light blue. Later in Season 4 and onward, her face was painted a lighter color and her eyes, whilst made much smaller, were equipped with an inner mechanism to move them around.
Rebecca is based on Jacques Cousteau's famous research vessel, RV Calypso. She represents several real research ships based at the Bedford Institute of Oceanography in Halifax such as CSS Hudson and CSS Acadia.
- Season 1 - Theodore's Bad Dreams, Theodore and the Queen (cameo) and The Big Harbour Clean Up Contest (cameo)
- Season 2 - Theodore Changes Sides (cameo), Night Shift, Whale of a Tug, The Tugboat Pledge (cameo), Hank and the Hug (cameo), Emily and the Rocket (cameo), Foduck Stays Home (cameo), Theodore in the Middle (cameo), Carla the Cool Cabin Cruiser (does not speak), Snorri the Viking Ship, Theodore the Jokester and Emily the Vigorous (cameo)
- Season 3 - Big Harbour Fools Day (does not speak), Grumpy Garbage Barge (cameo), Hank's New Name (cameo), Theodore and the Northern Lights (cameo), Big Harbour Birthday (cameo), Scally's Stuff (does not speak), Hank's Hiccups (cameo), Theodore's Big Friend (cameo) and George and the Underwater Mystery (cameo)
- Season 4 - Theodore's Ocean Adventure, Rebecca's Treasure, Hank Makes A Friend, Hank's Wheezy Whistle (cameo), Northumberland is Missing, and Rebecca and the Big Snore
- Season 5 - Hank Hurts a Ship, Bedford's Big Move, Theodore and the Missing Siren, Theodore and the Hunt for Northumberland (cameo), Emily Drifts Off (cameo) George and the Flags (cameo) and Hank Floats Forward (does not speak)
- Rebecca's engine that makes her move around the set was sold on eBay.
- Her wheelhouse is noticeably taller than that of her basis in order to accommodate her eyes.
- Out of all of the seasons, Rebecca didn't have a speaking role in the third season.
- ERTL (diecast; retired)