Do you know how to do drywall mud? If so you can float it down to the crown and texture/paint it. This will work up to maybe 3/4". More than that, get some 1/4" drywall and use it as filler first. If not, and you can do running trim, re-run the crown. If the gap is not much bigger than ~3/8" you can just caulk it.
Yes he did. I bet he’s fun as hell to hang out with too.