In Hello Kitty: Happy Party Pals Hello Kitty needs help to organize parties. The game consists of different levels (parties) that need to be planned. This includes inviting guests, gathering supplies and keeping everyone happy. The guests' happiness is shown through a percentage by talking to them, but it is also visible through a meter above their heads. If a certain rating is achieved Hello Kitty can move on to the next level. The game contains many Sanrio characters and it is the first Hello Kitty game for the GBA.
The first party is a small one in Kitty's playroom and she needs to invite two family members. Kitty can freely move around in the house to collect supplies such as a table cloth, a music disc, balloons etc. The gathered supplies are stored in a journal. The journal also shows who to invite. Kitty needs to do this by walking up to them and initiating a conversation. The guests are not always the same and items are not always in the same location. When talking to a potential guest their happiness rating is shown. By talking to them or giving items that rating can be improved, but only up to a certain level. The final part of the planning is decorating the room, with, for instance, the cloth and the balloons. Once the party starts Kitty can talk to the characters or play music to improve their happiness rating. The music needs to be matched with the guests. Old tunes will only make the elder people happy, but young people can for instance be given cake instead or you can play a game with them.
Many parts of the planning involve mini-games. Kitty can for instance make cakes. She needs to pour dough on a cooker with six burners, quickly flip them to prevent them from burning and then transfer them to a plate with a time limit of one minute. The second party takes place in the garden and Kitty can play the Bouncing Balloons mini-game in the sandbox, a Bust-A-Move clone. Based on the player's score various types of food are provided for the party. With each new party new environments are introduced, such as a garden, a park, an arcade etc. with more guests and items.
The third party is a park picnic. It has a mini-game that is a Concentration variant, matching identical cards. Guests can also be made happy by playing the Cutie Catch game. It is based on throwing a ball by determining the angle and the power of the throw so the other character can catch it and vice versa. The fourth party takes place at a Sushi restaurant and the fifth one at the Arcade. Other mini-games are a Dance Dance Revolution-like rhythm game, a sliding puzzle game, and designing custom invitations in a simplified art program, using images and colours that match the recipient's taste. Many items and activities return for the different parties. After each completed level a password is provided and it possible to access the thirteen mini-games right away from the main menu.