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, and as a compulsive workaholic, she neglects her physical health in the name of her occupation. 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.
In New Leaf
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.
In Animal Crossing: Happy Home Designer
Isabelle is an optional character who can move into the village where the player makes houses. She heads development of the town coming to you to help make certain places like a School, Cafe, Hospital, and Store.
In Monster Hunter 4 Ultimate
Capcom revealed outfits based on Isabelle and Mr. Resetti via its Unity blog, and confirmed that Felines' meow sound will be altered accordingly when they are equipped.
In Super Smash Bros. Wii U/3DS
Isabelle was confirmed to be an assist trophy character in Super Smash Bros. Wii U/3DS, 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 Taiko no Tatsujin: Atsumete Tomodachi Daisakusen!
In Taiko no Tatsujin: Atsumete Tomodachi Daisakusen!, Isabelle appears alongside with Tom Nook and Resetti as unlockable content via amiibo cards or figures being activated. Activating any Animal Crossing amiibo product may unlock other features from in-game features to soundtrack from Animal Crossing: New Leaf.
In Mario Kart 8
Isabelle has been confirmed as a DLC character, along with the Villager, for Mario Kart 8, and has been available since April 23rd, 2015.
Isabelle, alongside K.K. Slider, Tom Nook and Resetti, appears as a special costume after her respective amiibos are scanned.
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, which many did.
Advice for living in Town
Asking Isabelle for advice for living in the town is a sub-quest the player can do. She will repeat advice several times even if finished. Apart from listening to her advice, the player is asked to buy a shovel, collect one seashell and catch either three bugs or fish and eventually receives a basket of non-native fruit and a watering can. She does not always give this quest. If the player can't find a shovel and talks with Isabelle, she will give the player a shovel. She will also provide the player with either a net or a fishing pole in the same manner after asking the player to catch bugs or fish.
Depending on what the player's native fruit is, Isabelle will give the player a certain non-native fruit:
“Is there something I can help you with today?”
― Isabelle, offering the player assistance.
“Oh my! Has my clock gotten out of whack? Then please tell me what the correct time is!”
― Isabelle, when asked to set the clock.
“What?! Sorry, but my ears are just too fluffy and muffly, I guess. Please tell me once more.”
― Isabelle, after being told that the changed clock settings are incorrect.
“Oh, is that all? Well, we'll just.. WAIT, WHAT?! ”
― Isabelle, when asked to demolish the player's house.
“OK! The town will be... WAIT, WHAT?! ”
― Isabelle, when asked to delete the town.
“They want me in Smash?! (Isabelle turns over a new leaf!)”
― Isabelle, Isabelle being revealed in the 9/13/18 Nintendo Direct.
“I must say, I'm a fan of K.K. Slider myself...”
― Isabelle at the introduction spotlight, after Club LOL has been built.
Isabelle has her very own Twitter account at @animalcrossing, first used for sending news about New Leaf and later on for subsequent games. The account has sometimes temporarily been taken over by other characters with particular relevance to a certain game, such as Lottie with Happy Home Designer and Harvey with New Leaf's Welcome amiibo update.
Isabelle shares her birthday with Digby, since they're twins.
Her English name, Isabelle, possibly comes from the resemblance of her head to a bag of Bells (Isabelle = 'is a Bell'). She also wears a red ribbon with bells that jingle when she walks.
Her Japanese name, Shizue (しずえ?) may be interpreted as "quiet branch," perhaps referring to the tranquility of an Animal Crossing town. It can also be derived from her dog breed name "Shih Tzu".
Her Spanish name is Canela (Cinnamon), a symbol of wisdom and good health. "Can" (Can-ela) is also another word for dog in Spain, and it is used in the Spanish version of the game with her brother's name (Candrés) as a pun.
Her French name is Marie, a pun on the word Mairie (Town Hall) or Maire (Mayor).
Her Italian name is Fuffi, a pun on the fact that she is a dog.
Her Korean name, Yeoul (여울) means, "rapids" or "shallows" from a river.
Her Chinese name, 西施惠, possibly comes from the pronunciation of the Japanese name. "西施" also indicates the dog breed name "Shih Tzu". Its first appearance was on 13th of December, 2017, while the 1.4.0 update for Mario Kart 8 Deluxe was released.
Isabelle mentions that she still has cardboard boxes littered among her room, and is embarrassed to let Digby see. Isabelle in general may be a somewhat messy person, as Digby, who claims to be a neat freak, notes that while she isn't too messy, it's enough to get on his nerves.
One of the only ways to get Isabelle's coffee preference is through her twin brother Digby.
Isabelle changes her clothes starting on the second-half of October and ending at the 25th of February.
She is seen to sleep in Town Hall, and when the player goes up to the front of the counter, she wakes up with a surprised look on her, and then acts embarrassed.
Isabelle only has one tooth.
Isabelle mentions having a band upon completion of the concert hall in Happy Home Designer.
Isabelle has the voice of a peppyvillager, but her shown personality indicates that she is normal.
Talking to jock villagers will reveal some hidden depths to Isabelle's character:
They will sometimes that Isabelle taught them a new workout regimen where they pull weeds out from the ground, which, quite obviously to the player, is actually Isabelle shifting her duties to the villagers. This could hint to a possible mischievous side of Isabelle's character. More evidence to this side of Isabelle can be found in the Welcome Amiibo update, in which, after losing to Isabelle in Puzzle League, she will taunt the player by, as "leader of the Puzzle League," offering them a secretary position. Additionally, in Happy Home Designer Isabelle will playfully taunt Digby by calling him the "baby brother."
Jock villagers also mention that breaking a window will cause Isabelle to go "Isabellistic," hinting that Isabelle is not always as nice and respectful as she seems, and can be pushed into feelings of frustration, rage, and anger. This side of Isabelle has yet to be explored further in the series.
Sometimes if the player talks to her while visiting another town, she'll tell the player that she has many sisters who look exactly like her, that work as secretaries in other towns, and are all named, of course, "Isabelle". This could also be a reference to the Pokémon anime series where the character Nurse Joy keeps reappearing in all the towns the protagonist visits with the explanation being that they are all "identical cousins".
She has also appeared in a manga called Tobidase Doubutsu no Mori Minna de Seseragi Mura Life as one of the main characters.
When first announced, during the New Leaf developer commentary, Isabelle was not given a name, but was referred to as simply Secretary (ひしょHisho?), then named in the June 2012 Nintendo Direct as Shizue. Her name was changed in February 14th, 2013 at the Nintendo Direct to Isabelle, to localize her in English.
Sometimes if the player talks to her while she's visiting the campground in the Welcome amiibo update, she'll reveal she's actually nearsighted, hence why she wears glasses with her casual outfit.
She also mentions she wears contact lenses while working.
If the player talks to Digby in this update, he will mention that Isabelle occasionally takes road trips and claim she has a "terrible sense of direction", sometimes getting lost just walking around town hall.
Another dialogue option has her remark on how she's "rediscover[ed]" the beauty of the player's town, causing her to remark, "Technically, I think that makes this a work trip for tax purposes, right?" possibly hinting Isabelle commits tax evasion