(MICKEY)
Mickey is afraid of losing friends and family. After the loss of ortensia, and emotionally Oswald too, he feared this even more.

(GOOFY)
(//best Goofy impression//  fear? What's that?)
In all honesty, goofy is afraid of heights (I am aware he was a pilot.) But would put that fear away if he felt necessary.

(DONALD)
Despite how he is in recent cartoons (ducktales) he is afraid of taking responsibility for the loss of his sister (and therefore the triplets live with scrooge and are snobby rich kids //but not really//) and thinks poorly of kids.

(OSWALD)
He's afraid of his own emotional attachment to people. After the death of his beloved wife, he forced emotions away so he wouldn't have to deal with the pain of losing another loved one, such as Mickey.

(THE BUNNY CHILDREN)
All of them are scared of the dark. They're INNOCENT BABIES AND I COULDN'T HURT THEM I'M SORRY!

(It took all of what I had to write donald as a bad duck dad. I feel bad for it.. Poor donald. Hes a good uncle i swear (not dad jeez))