I'll post my answer again, only this time with the photo so you'll know what I'm referring to!
What you cannot see is the CM on the top of the mountain, most likely there to make sure Mickey makes it to the top okay. It must be hard to climb that mountain in that gear!
When I was a kid they would have regular mountain climbers climb the Matterhorn, but I never remembered Mickey doing it. This was definitely fun! They made a whole program out of it, broadcasting the characters talking to each other, etc.