In Swedish and Danish, it's "skål". I'm guessing it's still the same spelling in Norwegian (if we're right in thinking Mongster is Norwegian), since all three languages are close cousins. I definitely don't hear him using an "ö".
Anyway, there's your pedantic Swedish lecture for the day.
Edit: "ö" isn't even a letter in the Norwegian language. It would be "ø". Pedantic Swedish lecture Part II.
Once again led astray by my growing up watching the MN Vikings!