Belle is a minor character in Super Mario and the Underworld Trials. She, alongside her friends, appear in the Honeyhive Elementary course, and helps Mario and friends collect Mystic Stones throughout the area.
Belle, being a Bea, is a humanoid bee. She is a small girl with fair skin, and brown hair, with a ponytail held by a light-yellow scrunchie. Like all Beas, Belle has four brown arms; two on each side, as well as a pair of wings that can be used to fly. In addition, she has two yellow antennae on her head. Being a child however, her stinger hasn't developed yet. As a result of her exercise and activeness, her muscles have developed more than other Beas her age, making her look buff.
Belle's attire consists of a long, yellow dress with black stripes. This dress has a white turtleneck at the top. She also wears brown shoes. Like most Beas Belle also wears glasses, with hers being in a circle shape with light-yellow rims. In her pajamas, she instead wears a similarly-striped t-shirt with red sleeves, as well as blue sweatpants.
Belle is described as the most headstrong and most outgoing out of her circle of friends. Despite usually wearing a dress, she is a tomboy and has no interest in doing things she considers "too girly", such as playing with dolls or dress-up. As such, Belle takes more interest towards sports, such as soccer or basketball. She also has a competitive side to her, and is determined to win at anything in order to prove her superiority. Sometimes, this competitiveness can get so out of hand that she would resort to cheating or other underhanded methods. Belle also has a tendency to brag about her victories.
Despite this, Belle is generally friendly with others, and is quick to make friends. At times, she is also willing to put her friends before herself for their own benefit. Belle also calls herself the "leader" of the trio of friends, whereas Brooke and Brittany say that there is no defined leader.
Belle makes her debut in Super Mario and the Underworld Trials. In this game, she and her friends are found at Honeyhive Elementary, the fifth main course in the game, as third-grade students. They agree to help Mario and co. find the Mystic Stones throughout the area. Most of the course's Mystic Stones come from helping the three Beas, such as helping them win a relay race, helping them rid their clubhouse of intruders, and finding a stuffed animal at night. At one point, the three girls are held hostage by Bugaboom when he attacks the school, and they must be rescued by defeating the monster.
Belle reappears in Super Mario Kart: Switch Circuit as an unlockable playable character, marking her first appearance. In this game, she is in the super light weight class, having low top speed and weight, but having high acceleration and handling. Under normal circumstances, Belle must be unlocked by earning a three-star rank on all cups in the Mirror engine class, including the 8 Cup. However, if one has a save file of Super Mario and the Underworld Trials on their Nintendo Switch, she alongside Brooke, Brittany, Pearl, and Ruby become default characters. Belle's special item is the Mystic Stone, an item she shares with the aforementioned characters.
Belle also makes an appearance in The Rescue Squad: Birthday Blitz. In this game, she and her friends are found in Honeyhive Elementary, playing in their secret hideout. However, the Rescue Squad comes by and invites them to Pearl's seventh birthday party, which they agree to attend.
Belle appears as one of the playable characters in Sleepover Adventures. In the game, she is invited to Pearl's sleepover, and while sleeping, she dreams herself into the kingdom of Sala. However, she is then kidnapped and held prisoner in Screwtop Fortress in the Muna kingdom. Pearl manages to rescue her, and she joins Pearl on her quest to help the Sala kingdom win the war. She has a unique ability to use her wings to hover through the air, allowing her to reach higher areas.
Belle makes an appearance as a playable character in Super Mario Spikers, appearing as a Power-type captain. Her outfit consists of a gi with yellow and brown markings on the wrists and feet, and she additionally wears a black belt with a matching headband. Her emblem is a yellow bee and her theme is Ryūkōka.
Belle makes several references to the Street Fighter series in this game; her outfit is very similar to the one Ryu wears, she uses a move similar to Ryu's Hadoken attack, and her in-game biography states that she went through rigorous training to get her fighting prowess.
Belle appears as a newcomer in Super Smash Bros. Charged, debuting alongside Pearl. She is a lightweight with decent;y fast speed, and can achieve multiple midair jumps thanks to her wings.
Belle's moveset is a spoof of typical fighting game characters, such as Ryu, Ken, and Terry. She will always face her opponent in 1-on-1 battles, and her special moves have inputted versions that are stronger. However, in exchange for these versions being significantly stronger than Ryu's or Ken's, the button inputs are notoriously hard to perform. Additionally, like Terry's Super Special Moves, Belle has three other attacks that can be performed only with these special inputs, which are immensely useful and versatile if the player can input the buttons correctly. The moveset itself uses a combination of boxing, karate, and wrestling techniques. They are quite powerful despite her size, especially when the input attacks are taken into account.
She also has Brooke and Brittany as alternate costumes; while the Announcer and crowds refer to them by name and they have their own voice clips, they share no gameplay differences. Additionally, all three have their pajamas from Sleepover Adventures as an alternate costume.
Belle appears in Nintendo & Fantendo Play: Dodgeball! as part of the Green Faction, the team consisting of Nintendo fan characters.