For Disney, he was best known for voicing Piglet in the Winnie the Pooh franchise and currently holds the record for the longest running voice actor to ever voice a Winnie the Pooh character, having voiced Piglet for 37 years until his death. Fiedler's final role as Piglet was in Pooh's Heffalump Movie, released in February 2005, four months before his death.
He also voiced the Porcupine in The Fox and the Hound, the Deacon Owl in The Rescuers, Sexton Mouse in Robin Hood, and Rudy in The Emperor's New Groove. He even played Wally Thorpe in Midnight Madness and Charles Blackburn in The Whiz Kid and the Mystery at Riverton. Fiedler appeared in The Golden Girls episode "Love Me Tender", playing a love interest of Dorothy.
- Paul Winchell (the former voice of Tigger), incidentally, passed away on June 24, 2005, one day before Fiedler's death, at the age of 82.
- He was considered to voice Roquefort in The Aristocats, along with several other actors, but the role was ultimately given to Sterling Holloway.