facetiously       
adverb  disapproving uk/fəˈsiː.ʃəs.li/ us/fəˈsiː.ʃəs.li/
 (尤指不问场合)好开玩笑地;滑稽地,诙谐地
in a way that is not serious, in an attempt to be funny or to appear clever about a serious subject 
  She facetiously challenged him to a ski race.  她开玩笑地向他挑战来一场滑雪比赛。 
 The finale of the film comes off facetiously. 这部电影的结局很滑稽。 
 See: facetious
 - More examples
 - The passages were written facetiously.
 - Washington Irving's "Knickerbocker History of New York" facetiously begins with the creation of the world.
 - He facetiously suggested banning Viking attack boats and hot air balloons.