Amelia Fieldmouse is an anthropomorphic mouse who is Mickey Mouse's sister and Morty and Ferdie's mother, also unofficially the half-sister of Oswald the Lucky Rabbit. The character has only appeared in comics.
She first appeared in Morty and Ferdie's 1932 debut strip, Mickey's Nephews, as a woman arriving at Mickey’s house (Mrs. Fieldmouse) and dropped the twins off and asked if he would not mind caring for them while she ran an errand. In the Dutch comic strips, her name is translated as “Amelia”, in the English version she is referred to as “Mrs. Fieldmouse. The original strips do not make clear that Amelia is Mickey's sister; as drawn, she looks more like a maiden aunt. But the relationship has been clarified when she reappeared in more recent comics. At Egmont Publishing, Amelia's name is given as "Felicity Fieldmouse". As a side note, Egmont also named Felicity's husband—the twins' father—Frank, though he has yet to be specifically named or depicted in a published comic. Egmont's modern version of Amelia has slimmed down and is designed to look closer to Mickey in age, while remaining significantly taller than him.