Yellow Toad (Toad Brigade)

Super Mario Sunshine
Yellow Toad first appears in Super Mario Sunshine, where he is one of the five young Toads that accompany Mario, Princess Peach, and Toadsworth on their vacation to Isle Delfino. Upon arrival, the group finds the island a mess. Soon after, the villain Shadow Mario appears and kidnaps Peach. This causes the Toads (Yellow Toad among them) extreme sadness and worry. The Toads provide no help, as they spend most of their time in Delfino Plaza. Yellow Toad is usually found alongside Purple Toad and Toadsworth; often running around worrying about the Princess. Out of the six Toads in the game, these three tend to worry the most. In the ending, the Toads are shown to be much happier as Mario rescues Peach and cleans the island. Yellow Toad is seen enjoying himself during the end credits alongside the other Toads.

Mario vs. Donkey Kong
Yellow Toad reappeared in Mario vs. Donkey Kong, where Red Toad, Blue Toad, and he were employed at the toy store. They worked joyfully, enjoying the Mini Mario toys that were produced there, until Donkey Kong arrived and stole them. After Mario defeated Donkey Kong in Twilight City Plus, Yellow Toad could be seen alongside Mario, the Mini Marios and the other two Toads, apparently laughing at Donkey Kong, who had lost all of the Mini Marios that he stole. In his anger, Donkey Kong grabbed the three Toads and climbed up on top of a tall tower. However, Mario would defeat him again and save the Toads.

Super Mario Galaxy
Yellow Toad appeared in Super Mario Galaxy as one of the members of the Toad Brigade. Out of the group, Yellow Toad seemed to be the most careless and lazy, as he is often seen sleeping in the game. For this trait, he received from the other Toads the nickname "Sleepy." However at times when he is not asleep, Yellow Toad can be seen as a rather immature character as seen in the Purple Coin challenge in Deep Dark Galaxy where he is seen dancing under a spotlight while the other Toads stayed around the area cautiously. After assisting Mario on his quest, the members of the Toad Brigade (including Yellow Toad) were revealed to being promoted to Royal Guards of Princess Peach's Castle.

Personality
Yellow Toad like many other characters in the series is still a rather undeveloped character. His personality is often seen changing in many of the games that he does appear in. In Super Mario Sunshine, he is seen as a rather worrisome character despite the fact that he is meant to be a jolly character as seen in the intro. In Super Mario Galaxy, he is shown to be a rather lazy character as he is seen sleeping for nearly the whole game. New Super Mario Bros. Wii, however showed a direct opposite personality in comparison to his worrisome self in Super Mario Sunshine as he is able to bravely join the Mario brothers on their journey to rescue Peach.