We are accustomed to seeing elevators frequently in our everyday life; however, this situation is not so common as the elevator is actually a phone, Mickey pulls on the cord to simulate requesting a floor and the ring emulates the sound an elevator makes.
Aside from the obvious fact that cards are inanimate, and as cool as the spring move is, it is not possible. The cards look awfully thin and would not have the strength to move a mouse or the coordination to; however, this makes sense to us as the viewers because we are used to seeing accordion or spring effects.
A mouse would not be thin enough to be shuffled into a deck not to say that it couldn't be shuffled but it wouldn't be this smooth. They were still able to accurately portray Mickey giving him the qualities of the cards.
Owning a fountain pen myself, it is possible to have a leaky pin; however, weaponizing it and projectile squirting ink is not possible. The animators created a wartime scene making the basket look like a barricade and giving Mickey a helmet making it plausible.
Finally, the cards are incapable of removing the markings printed onto them and throwing them. The animators make this seem plausible by continuing the wartime effect.
