they probably BOTH had a wonderful sense of humor but how would it look for a prophet/savior to be able to make people laugh AND share the word of God/Allah? Most likely not too good, so us being humans, took out the human side of each of them and put it into writing that they were always serious....

However..if you ever wonder about God/Allah having a sense of humor..just take a look at how He put together the giraffee...and it will remove all doubt!!

Grant me the senility to forget the people I never liked,the good fortune to run into the ones I do,and the eyesight to tell the difference.