- "I heard a creature called Tessie lives in the southern lake... I don't believe it! I think someone made a model and placed it in the lake."
- — Snow Wood Boarding School student
Tessie (Tassy) is a character in EarthBound. She is a friendly, long-necked monster which lets Jeff Andonuts and the Bubble Monkey ride on her back to cross Lake Tess in Winters. There is an entire club called the Tessie-Watching Club that are dedicated to finding and seeing Tessie, but ironically, they never seem to notice the few times where Tessie comes out to carry Ness's party on its back.
- Tessie was inspired by Nessie, the Loch Ness Monster. This is referenced in-game when a Hotel employee accidently buys the TwosonStar newspaper instead of the Twoson Tribune, which has the headline "Tessie in Lake Tess is cousin of Nessie".
- During the events of Mother 3, Tessie can be seen in the Hall of Memories in New Pork City's Empire Porky Building.
- In the Mother 1+2 Art Book, several pictures of Tessie were included that showed significant changes as to the way Tessie is ridden across the lake; Jeff was originally planned to either have his boat lifted out of the water on Tessie's head or stand on one of Tessie's humps. However, a third image shows a scene similar to the final version with both Jeff and the Bubble Monkey walking towards Tessie's ripples.