Spike, serving as Twilight's assistant, moves with her to Ponyville in Friendship is Magic, part 1 when Celestia orders Twilight to go for the Summer Sun Celebration. Twilight is slightly depressed, but Spike tries to cheer her up, telling her that the Princess arranged for her to stay in a library. Throughout the series he sends correspondence between Twilight and the Princess using his magical fire breath, helps organize and fetch books, reads and writes letters, keeps Twilight's checklists, and helps her practice magic. In one instance, he is "away on royal business", in Look Before You Sleep.
Spike finds Twilight her "old copy of Predictions and Prophecies", re-shelves Twilight's pile of books, and checks off items in her Summer Sun Celebration checklist in Friendship is Magic, part 1. In Griffon the Brush Off, Spike got the scrolls from town-hall. He helps Twilight practice magic in the beginning of Boast Busters and also in Feeling Pinkie Keen. Also, in the aforementioned episodes, Spike takes notes for Twilight and carries the books from the library. In Bridle Gossip, Spike both offers the book "Super Naturals" and stays at the library to look for a cure to the ponies' "curse" while they go to Zecora's. In Owl's Well That Ends Well, he prepares a picnic entirely by himself, and later accidentally burns a book he was supposed to put back in place. He tidies up the library in The Return of Harmony Part 2. He fills so many checklists in Lesson Zero that he gets a claw-cramp, and carries a broom at the library in Read It and Weep. He's only in 3 generations of mlp.