"Yoshi (ヨッシー, Yosshī, sometimes romanized Yossy in earlier Japanese materials) (IPA: /ˈjəʊ.ʃi/) is a fictional dinosaur. His debut was in Super Mario World on the Super Nintendo Entertainment System as Mario's accomplice, and he later established his own series with several platform and puzzle games, including Super Mario World 2: Yoshi's Island. He has also appeared in many of the spin-off Mario games, such as the Mario Party, the Mario Kart, and the Super Smash Bros. series , as well as in other various Mario sports titles. Most recently, Yoshi appears in New Super Mario Bros. Wii as the characters' accomplice, similar to his original debut role in Super Mario World. Yoshis come in many different colors, but his original and most common color is green. Yoshi is set to appear in the upcoming Super Mario Galaxy 2."
Source: Wikipedia, "Yoshi", available under the CC-BY-SA License.