Yoda was voiced by Frank Oz in the five films that he appeared in. For the original trilogy and in the original Phantom Menace Yoda was a puppet, but he was also portrayed in some shots by Warwick Davis (who also played Wicket, Yoda's opponent today). Yoda was changed to CGI in the final two prequel films for better movement, and later changed to CGI in Phantom Menace. Fun Fact: Yoda was originally a last name as he was originally named Minch Yoda.
Wicket was portrayed by Warwick Davis during the Return of the Jedi and also in the two spinoff Ewok films. Fun Fact: Kenny Baker, who plays R2-D2, was originally scheduled to play Wicket, but when the time came for him to interact with Princess Leia, Baker fell ill. So, Davis' Ewok stepped up to the plate and eventually became known as Wicket. Baker played the Ewok, Paploo.