Petra is one of the Big Harbour's two pilot boats who patrol the harbour and sometimes help the tugs with moving ship to their docks. They both used to have a problem with not listening to the tugboats, which caused a lot of confusion.
Petra was the second pilot boat to come to the harbour and has a closer relationship with the tugboats, having more of a kind, supportive side than Pearl. She was a bit shy at first about coming to the Big Harbour until Theodore introduced her to everyone. She also enjoys playing "hide and surprise" with Theodore and Barrington on occassion.
Both Pearl and Petra are hard working and work together with the tugs to keep the harbour running properly.
- Season 1 - Theodore and the Homesick Rowboat, Foduck the Vigilant (not named, does not speak), Hank and the Mermaid (cameo), The Day Ice Came to the Harbour (mentioned), Theodore's Bad Dreams, Is Anybody Listening?, and Theodore and the Big Harbour (mentioned)
- Season 2 - Night Shift (cameo), The Tugboat Pledge (does not speak), The Cold Snap, Foduck Stays Home (does not speak), Theodore's Day Off, and Foduck and the Rainbow
- Season 3 - All Quiet in the Big Harbour (cameo), A Joke Too Far, Hank's Hiccups (cameo), Big Harbour Birthday Emily's New Hat (cameo), and Theodore and the Pirate
- Season 4 - Foduck's Hurt Feelings (cameo)
- Season 5 - Bedford's Big Move (does not speak), George Waits His Turn (cameo) and Hank Floats Forward
- Petra is the youngest of the two pilot boats.
- Petra's model was one of the few models to be sold complete on ebay.
- Petra was much stricter in the first season.
- The back wheel of her wheel chassis is simply a desk chair wheel.
- In Theodore and the Pirate, Petra was introduced, but she was seen in the first season and the second season which both took place before Theodore and the Pirate.
- Out of all of the seasons, Petra didn't have a speaking role in the fourth season.