Well, it's been a while since I did a cast list. So here goes for my Fantasia Fanmakes (First Segment & The Soundtrack don't actually count for me since they're exceptions and visuals). Also, don't hate me for these decisions. This can be done, hopefully:

AniTasia:
UPDATE: Host Deems Taylor-Joe Leahy (Freakazoid) (thanks to Jus for helping me out)
UPDATE: Leopold Stokowski-Mr. Persnickety (Mr. Men)
Sprites & Fairies (in Nutcracker Suite)-Tinker Bell & Disney Fairies (Disney Fairies & Peter Pan)
Mushrooms-White Mushrooms (Kingdom Hearts)
Flowers & Russian Thistles-Plant Pokemon
Goldfish-Goldeen (Pokemon)
Mickey-Buster (Tiny Toons)
Yen Sid-Bugs (Looney Tunes)
Brooms-Woodmon (Digimon)
Dinosaurs-Digimon
Centaurs-Various Crossover Couples
Cupids-Cupid, Cosmo, Wanda, & Poof (Fairly Oddparents)
Horned Donkey-Donkey (Shrek)
Fauns-Timmy, Chester, AJ, & Elmer (Fairly Oddparents)
Pegasus-Flutter Ponies & Pegasus Ponies (My Little Pony)
Unicorns-Unicorn Ponies (My Little Pony)
Bacchus-Mr. Scatterbrain (Mr. Men)
Zeus-Mr. Rude (Mr. Men)
Vulcan-Mr. Strong (Mr. Men)
Apollo-Mr. Happy (Mr. Men)
Iris-Miss Sunshine (Mr. Men)
Morpheus-Miss Whoops (Mr. Men)
Diana-Miss Helpful (Mr. Men)
Hyacinth Hippo-Kate (Sailor Moon/Great Mouse Detective OC)
Ben Ali Gator-Ratigan (Great Mouse Detective)
Hippos-Half Breed Humans of Toon Characters
Alligators-Various Rats (probably Organization XIII as rats)
Ostriches-Various Cats
Elephants-Donphan (Pokemon)
Cherneborg-Nightmare King (Little Nemo)

AniTasia 2000:
Abstract Butterflies-Butterfree (Pokemon)
Steve Martin-Chris (Total Drama Island)
Itzhak Perlman-Chef (Total Drama Island)
Whales-Sea Pokemon with Latios & Latias
Quincy Jones-Miroku (Inuyasha)
Duke-Manic (Sonic the Hedgehog)
Rachel-Rini (Sailor Moon)
Mom & Dad-Serena & Darian (Sailor Moon)
Tutor-Endive (Chowder)
Jobless Joe-Mr. Nervous (Mr. Men)
Flying John-Snoops (Rescuers)
Killjoy Margaret-Madam Medusa (Rescuers)
Foo Foo-Pet Gators Brutus and Nero (Rescuers)
Bette Midler-Sango (Inuyasha)
The Tin Soldier-Hans Drosselmeyer (Nutcracker Prince)
Ballerina-Clara (Nutcracker Prince)
Jack-in-the-Box-Farquad (Shrek)
James Earl Jones-Anakin (Star Wars)
Punkin-Funny Bird (For the Birds)
Snotty Six-Squeaker Birds (For the Birds)
Penn & Teller-Penn & Teller (Mucha Lucha version)
James Levine-Inuyasha (Inuyasha)
Donald-Plucky (Tiny Toons)
Daisy-Shirley (Tiny Toons)
Noah-Noah (Great Adventures from the Bible (yes I did see this series))
Angela Lansbury-Kagome (Inuyasha)
Sprite-Cosmo (Sonic the Hedgehog)
Elk-Great Prince (Bambi)
Firebird-Moltres (Pokemon)

That's it for the cast list. Hope you enjoy it.