The Yoshi series is a series of games that star Yoshi, who was introduced to the Mario games in Super Mario World. Though he has his own series, Yoshi does still appear quite frequently in the Mario series. The Yoshi series includes characters from the Mario series, (usually as their baby forms), as well. Both series take place on Mushroom Kingdom in two different timelines; the past and present.
The Yoshi series' plot has varied greatly over the years. The main titles generally revolve around the kidnapping of Baby Luigi. Baby Mario must then be escorted and protected by Yoshis as he traverses through several worlds to rescue his younger brother. Yoshi's Story was the first main game that did not feature the Mario Bros. in any way other than a brief mention.
The other titles have varied somewhat in plot as well. While Yoshi and Yoshi's Cookie were Tetris-like puzzle games with no actual plot, Yoshi Topsy-Turvy had an entirely different story from both the main and puzzle titles. This game revolved around Yoshi having to rescue his island which had been turned into a storybook. In Yoshi Touch & Go, no concrete plot was revealed, similar to the puzzle games.
Yoshi Series Games
Tech Demos and Cancelled Game
Major elements of the Yoshi series
Colors of Yoshis
The following table gives an example of each color Yoshi that inhabits Yoshi's Island, and in which games it appears.