Some extra info on some of the "missing links" on your list, courtesy of Wiki.
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Fun and Fancy Free comprises of TWO stories:
Bongo: The story of a circus bear cub, who runs away from the circus to the wild and the adventures there that follow. This was based on an original story by Sinclair Lewis.
Mickey and the Beanstalk: An adaptation of Jack and the Beanstalk with Mickey Mouse, Donald Duck, and Goofy as peasants who discover temperamental Willie the Giant's castle in the sky through the use of some magic beans.
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Melody Time also has several segents, some of which are based on previously written work:
- Once Upon a Wintertime features Frances Langford singing the title song about two romantic young lovers in December. The boy shows off for his girl, and near-tragedy and a timely rescue ensue. This short was also featured in Very Merry Christmas Songs which is part of Disney Sing Along Songs as a background movie for the song Jingle Bells.
- Bumble Boogie is a surrealistic nightmare for a solitary bee trying to escape from a visual and musical frenzy. The music is courtesy of Freddy Martin and his orchestra (with Jack Fina playing the piano) and is a swing-jazz variation of Rimsky-Korsakov's Flight of the Bumblebee, which was one of the many pieces considered for inclusion in Fantasia.
- The Legend of Johnny Appleseed is a retelling of the story of John Chapman, who spent most of his life roaming America and planting apple trees, thus earning his famous nickname. Dennis Day narrates and provides all the voices.
- Little Toot is based on the poem by Hardie Gramatky, in which the title protagonist, a small tugboat, wants to be just like his father but can't seem to stay out of trouble. The Andrews Sisters provide the vocals. Out of all the musical segments, this one is the most famous.
- Trees is a reciting of the famous Alfred Joyce Kilmer poem by Fred Waring and the Pennsylvanians with the lyrical setting seen through the seasons.
- Blame It On the Samba has Donald Duck and Jos