"Pluto and the Armadillo" from 1943 is the last Mickey Mouse Cartoon, as well as Cartoon featuring Mickey for a period of three years until the next Mickey Mouse Cartoon "Squatter's Rights (1946)" from 1946.
"Pluto and the Armadillo" from 1943 marks the final appearance of Mickey in his iconic red two-button shorts. Mickey in his red shorts wouldn't be seen again in animation until the 1988 TV film "Mickey's 60th Birthday (1988)" for Mickey's 60th Birthday Celebration in 1988, as well as his later cameo appearance in "Who Framed Roger Rabbit (1988)" and again for the first time in a Mickey Mouse Cartoon in "Runaway Brain (1995)" from 1995.
"Pluto and the Armadillo" from 1943 was inspired by the Disney artists' goodwill tour of Latin America and was originally set to be included in "Saludos Amigos (1942)" from 1942 accompanied by a live-action segment on a Brazilian zoo. Some footage of an animator drawing the armadillo, as well as a pencil test of the armadillo's walk, is featured in the documentary short film "South of the Border with Disney (1942)" from 1942.
"Pluto and the Armadillo" from 1943 is considered to be the last Mickey Mouse Cartoon in which he has his perspective ears and experimental character design, that he had since the 1941 Mickey Mouse Cartoon "The Little Whirlwind (1941)". He would return to his traditional character design in the 1946 Mickey Mouse Cartoon "Squatter's Rights (1946)". However, it seems from the brief glimpses we get to see of Mickey's ears, since they are covered by his hat for the majority of time, that they are already reverted to his regular iconic moving ears. One notable indication of this is that he has his tail back again, which was removed with the experimental design.