After you kill olimar & reset, pick charizard first for the duon fight. It'll be way faster to do it with charizard & then right after that it takes your to the Halberd where you can quickly SD off the side and it'll switch you back to MK literally in front of the door you need to go in.

ya know there was a point where i like wanted to use Charizard there but i didnt realize that you could SD right after 🤷

You can also pick charizard before fighting Petey and have the same kind of affect, but idk what the time save on it actually is.

as an example

Looks to be 3-5 seconds if done right