Animation producer/director Arthur Rankin, Jr. tells the story behind Rudolph the Red-Nosed Reindeer, including the fact that an actor other than Burl Ives was originally cast as “Sam the Snowman”:
”We put the track together with this actor as ‘Sam the Snowman.’ And afterwards, we realized we needed and wanted Burl [Ives]. Contacted him, he said he'd do it. We arranged to have him re-record all those sections. …He came in and saw the action-- saw the storyboard, saw the character, and did his part. We then cut him in and took the other actor out. And we had a star."
Watch Arthur Rankin, Jr.’s full interview, which spans his career, including creating the classic animated specials The New Adventures of Pinocchio and Rudolph the Red-Nosed Reindeer.