The Wizard of Oz Disney Cast

Dorothy - Belle (Beauty and the Beast)
Toto - Jock (Lady and the Tramp)
Glinda - Blue Fairy (Pinocchio)
Wicked Witch of the West - Maleficent (Sleeping Beauty)
Myra Gulche - Lady Tremaine (Cinderella)
Cowardly Lion - Simba (Lion King)
Tin Man - ???
Scarecrow - Tigger (Winnie the Pooh)
Wizard - Merlin (Sword in the Stone)
Wizard (fake) - Magic Mirror (Snow White)
Aunty Em - Widow Tweed (Fox and the Hound)
Uncle Henry - Amos Slade (Fox and the Hound)
Munchkins - Mice (Cinderella)
Flying Monkeys - King Louie and Co. (Jungle Book)
Talking trees - Trees (Snow White)
Horse of a different colour - Pegasus (Hercules)

That's something like what I'd do. :)

The Widow from the Fox and the Hound should be Auntie Em, Merlin should be the wizard, and Amos should be Uncle Henry. Btw this is a wonderful idea! Ive loved this movie since I was little.

maleficent as the wicked witch
mickey mouse in the sorcerer's apprentice as the wizard
tigger as the scarecrow
beast as the tin man
fairy godmother in cinderella as aunty em

i think what you have so far is great too!!!

alice as dorothy
jock as toto
simba as the cowardly Lion
merryweather as glinda
madame mim as witch

I think the Fairy Godmother in Cinderella is a good choice for Glinda as well. I've never seen Pinocchio so I can't vouch for the Blue Fairy.
I think either Alice or Belle may be a better Dorothy. They're already dressed similar, and I don't see any similarities between Melody and Dorothy.
I say Beast as the Cowardly Lion.
And I like the Mirror as the Wizard.

I will try to think of who could be potential Tin Men, Scarecrows, and or Flying Monkeys and edit when I do.

Btw I really like this idea and I think you have pretty good choices so far.

edit: Y'know that talking apple tree? One of the trees in Snow White could be that... I think that's kind of an unnecessary character but I just thought of it...

edit2: The Vultures in The Jungle Book as Flying Monkeys?

ok, I have a few ideas (I didn't read the other suggestions, so if I repeat ideas, sorry)

since Frank Morgan played Professor Marvel/The Gatekeeper/The Carriage Driver/The Doorman and The Wizard of Oz in the movie, you could have one character do all of those too

(I think stitch would be a good Toto, just to mix it up)

the flying monkeys could be monkeys from Tarzan or Jungle Book

my sister thinks goofy should be the scarecrow, so if that happened, I would think mickey could be the tin man and donald the cowardly lion

hope that helps

Dorothy: Alice or Belle
Scarecrow: Goofy or Roger Rabbit
Lion: Simba (coz he's a lion) or Pumbaa (coz he's easily scared)
Wicked Witch: Maleficent or Hag from Snow White
Wizard Head: Magic Mirror
Wizard of Oz: Merlin or Genie
Toto: Jock, Scamp, or Bruno (cinderella's dog)
Miss Gulch: Lady Tremaine
Auntie Em & Uncle Henry: Widow Tweed & Amos Slade
Glinda: Cinderella's fairy godmother, blue fairy, or Tinkerbell
Munchkins: 7 dwarfs, 3 nephews (Huey, Dewey, Louie), Mickey, Minnie, Lost Boys, Pinocchio

Tin Man is hard to pick but I can only suggest Hugo (from the Hunchback of Notre Dame)or even Donald Duck but if you run out of options go pixar and pick Wall-E

I agree with Mongoose09. But isn't it rather difficult to do a whole movie? Can you send me the link of the youtuber?