Isabelle is very clumsy and absentminded and dislikes confrontation. Despite this, she is respectful of others and is very friendly. Being open-minded and friendly, she is very keen to make the town a better place to live, by encouraging the player to do tasks and Public Works Projects throughout the town. Like many other secretaries, she can be hard on herself when she is side-tracked. Isabelle has shown sides of gratitude and affection to the player, especially on Valentine's Day and is even hinted on having a crush on the player regardless of gender.
Isabelle is a nearsighted bright yellow dog who resembles a Shih Tzu, which her Japanese name, Shizue, is a play on. Her head is also shaped like a bag of bells, hence the English name. She has a happy appearance with rosy cheeks and with a white fur patch on her tail and around her mouth. She wears a green checkered vest with a white top and a red ribbon underneath with a navy blue skirt. During fall and winter, she wears a yellow cardigan instead of a vest. Her hair is tied up with a red elastic with bells attached which actually jingle as she walks.
She wears different styled clothes on special events that are held around the town; for example, she will wear a flowery shirt during the Fireworks Show and a Santa-style shirt on Toy Day.
Mario Kart 8
Super Smash Bros. 3DS/Wii U
Isabelle was confirmed to be an assist trophy character in Super Smash Bros. for Wii U, on the 4th of March, 2014 in the Wii U version (although she is also present in the 3DS version). She was shown again in the Super Smash Bros in the Nintendo Direct on the 8th of April. Later on, she was confirmed that she will help the fighter who summoned her by throwing fruit towards them that can be 'eaten', lowering their percentage but fighters cannot interact with her. An Isabelle Suit for the Mii Gunner was included as part of Smash Bundle #2 as well.
In Super Smash Bros. Ultimate
On September 13, 2018, Isabelle was confirmed to be a playable fighter in Super Smash Bros. Ultimate for the Nintendo Switch. In her reveal trailer, she is seen working around the mayor's office while the mayor is out camping and fighting in Smash. She then gets a letter from Pete and is shocked when it ends up being an invitation for Smash. Her trailer ends asking for the viewers to cheer her on.
- Isabelle is the third Assist Trophy to become playable in the Super Smash Bros. series, after Little Mac and Dark Samus.
- Isabelle is the fifth playable canid character after Fox McCloud, Wolf O'Donnell, Lucario, and the Duck Hunt dog, as well as the first female dog.
- Isabelle is also the first playable anthropomorphic animal to be female.