Toadsworth makes his first appearance in Super Mario Sunshine where he accompanied Mario, Princess Peach, and a bunch of Toads to Isle Delfino for a vacation. At first he simply accompanies the Princess around the island. After she is kidnapped by Shadow Mario, he can be found fretting and worrying in various locations. After she is rescued he returned with the rest of the vacationers to the Mushroom Kingdom.
In Mario & Luigi: Superstar Saga, Toadsworth makes a brief appearance in the beginning of the game where he presents Mario and Luigi with a Suitcase. Later he comes to the Beanbean Kingdom himself (along with Princess Peach). After a while, he spends his time with Peach in the Mushroom Embassy.
Toadsworth makes another cameo appearance as the referee in Mario Power Tennis.
Mario Baseball series
Toadsworth accompanies Princess Peach on her trip to Rogueport during Paper Mario: The Thousand-Year Door. He keeps Princess Peach very close to him, but ends up losing her. When Mario comes to Rogueport he meets a frantic Toadsworth who is incredibly worried about the missing Princess. Mario assures Toadsworth that he will save her, and Toadsworth spends the remainder of the game in Rogueport's Inn.
In Mario & Luigi: Partners in Time, he is with Mario and Luigi when Princess Peach takes an experimental trip back in time with Professor E. Gadd's time machine, and is paranoid that something terrible will happen. His fears later become justified, as when the time machine returns a Shroob is in it. Before that, however, he promptly faints, and requires a Refreshroom to revive him. He is still confused when he wakes up and accidentally pushes Mario and Luigi into a time hole. He later teams up with his younger self to teach the Bros. new moves and keep Baby Peach entertained while she stays in the future. He is last seen in the game when he, Mario, Luigi and Peach bid his younger self and the babies goodbye who are going back to their time.
Toadsworth appears in Mario Party 7 as the main host of the boards.
Toadsworth is a very elderly Toad. He is very protective of the Toads and is very kind (except when the Toads are in danger). Also, Toadsworth is shown to care very deeply for Princess Peach and protects her as she is his own very own daughter. Whenever Peach is captured (which, given Bowser's track record, happens a lot), Toadsworth gets very upset and usually blames himself or Mario and Luigi for not protecting her at the time.