Film is 24fps, not 25. You generally shoot everything “on twos”, which is to say that you expose a single drawing twice, for an effective frame rate of 12fps.

There are places you go on ones. Fast motions, motions that need to be ultra-smooth. Ideally you also shoot pans on ones, and the walk cycles you use on top of pans are drawn to match. But you can get away with doing them on twos.

If you watch the sequence you can also see several places where Mickey is performing the same action over and over. When he’s walking to the side it’s the same eight or sixteen drawings shot in a loop. When he’s standing there’s twirling his tail, that’s its own set of repeated drawings. The part where Mickey turns and walks off into the distance might be another couple of 8-drawing cycles that were photomechanically scaled up and down, then manually inked and painted.

It is also quite possible that only part of this sequence was done to match up with Walt’s narration; easy enough to start with parts made for a short. Even without that there’s realistically only about 10s of unique drawings here, if you shot them one after another on twos.

You can get by with less drawings, too. My experience is that 10fps is as low as you can go and still have the capability of smoothish motion. You can go lower; Asian animation typically uses a LOT fewer drawings for most of a show than the high-frame-rate work of a 50s Disney piece. And then you get one sequence where they blow the budget, with complex characters (who require like 4x the work to draw a single frame compared to Mickey) moving around.

(I used to work in animation.)