I couldn't agree more that humor plays a huge role in terms of the classroom, not just in motivation, but also with memory! The funny teachers always have the best students in terms of behavior and overall grades. Sometimes though, teachers can get too carried away, which leads to a more disruptive class as they are viewed as the "slack" teacher, but adding an air of humor/comedy to the material keeps everyone interested.
In terms of memory, how many times have you heard "You need to find a way to 'relate' to the material in order to remember it." That always bugged me, because I didn't understand exactly what it meant. It took some self research to discover my own way of "relating" to material, by means of incorporating humorous storytelling to myself. By making a sort of funny story in my head that included the information I was trying to learn, it made it a million times easier to remember! By tying an event to an emotion, you will remember it forever. (See Mark Gungor's YouTube video "Tale of Two Brains")
For example, trying to remember the names of the Great Lakes in Canada for my Geography class seemed silly, short of re-reading the real names over and over again. So we always made a funny acronym for it; Sam Made Harry Eat Olives! Superior, Michigan, Huron, Eerie and Ontario! Chuckles to self for remembering after all this time
So the next time you or even your son/daughter is having trouble remembering dates/names/equations, make a funny rhyme, or a funny story, or create a funny character in their head for them to remember. The more visual the better! That way, they can just recall the funny story, and the information will follow. Hopefully that makes sense!