A brief overview of the characters in Super Mario 64.
Major[ | ]
Mario is the main protagonist in Super Mario 64. He received a letter from Princess Peach, asking him to come to the castle because she baked a cake for him. Mario jumps out of the warp pipe, and heads off to the castle. Once inside, he is greeted by a message from Bowser, warning him that he captured the Princess and to find her, he must retrieve the Power Stars from the levels. Mario has a ton of unique abilities in this game, from a baseball slide, to a long jump, and even being able to jump off walls! Eventually, Mario collects a good chunk of the Power Stars and eventually heads off to fight Bowser (for the third time). Once Bowser is defeated, Mario rescues Peach shows her gratitude by giving him a kiss and they go off to eat cake.
Bowser is the main antagonist in Super Mario 64. He has captured Princess Peach and is hiding her in one of the paintings somewhere inside the castle. He warns Mario as soon as he enters the castle that he'll have to collect Power Stars to reach her. Bowser fights Mario a few times in the level. He is able to jump up high and stomp on the ground, and breathe fire, and teleport, and survive being thrown off the stage. He does, however, have a weak spot: the spiked bombs littered around the arenas. He becomes progressively harder with each fight, the third fight being the hardest. It takes Mario three hits to defeat Bowser in the last fight, and once he's defeated, the giant Power Star is unleashed, and Peach is rescued.
Peach appears very briefly in Super Mario 64. She appears in the opening sequence, delivering a letter to Mario, asking him to stop by the castle to enjoy some cake. Unfortunately, Bowser managed to capture her and hide her in one of the paintings within the castle walls. Mario eventually rescues Peach and she rewards him with a kiss, and then they go off to eat cake. Interestingly enough, Peach refers to herself as "Princess Toadstool" in the opening note.
Minor[ | ]
Toad appears many times throughout Super Mario 64. He often give Mario advice and tips on gameplay. He even manages to find a few Power Stars. It is unknown if there are multiple Toads in the castle, or just the same Toad in each location.
Yoshi appears in Super Mario 64 on top of the castle, once Mario has collected all 120 Power Stars. He rewards Mario with maximum lives, and delivers a message from Nintendo staff, thanking the player for playing.