facetiously

adverb2

1. •
   In a facetious or flippant manner; in a manner that treats serious issues with deliberately inappropriate humor.

   • Pirates are revered as the original Pastafarians, and Pastafarians facetiously assert that a steady decline in the number of pirates has resulted in a significant rise in global temperature. — 2010
2. •
   (old-fashioned) In a pleasantly humorous or playful fashion.