Complex sentence: Bolger's MGM contract stipulated that he would play any part the studio chose; however, he was unhappy when he was originally cast as the Tin Woodman in the studio's 1939 feature film adaptation of "The Wizard of Oz".
Split into simpler sentences: Bolger's MGM contract stipulated that he would play any part the studio chose. However, he was unhappy when he was originally cast as the Tin Woodman in the studio's 1939 feature film adaptation of "The Wizard of Oz".