I’m pretty sure this has been discussed before, but before I look at anything others have said…
Kermit and Miss Piggy are the obvious choices for Westley and Buttercup. But I also kind of want to use Kermit and Robin for the Peter Falk and Fred Savage roles.
Pepe the Prawn could be Vizzini.
Dr. Bunsen Honeydew and Beaker as Miracle Max and his wife.
Statler and Waldorf filling in for the old lady in the dream who shouts “Boo!”
Now, some links to suggestions that have been made before: