http://www.buzzle.com/articles/glossary-of-literary-terms.html#H
Scroll down and read the entry for Humor. See if there's the term you're looking for.
What is the literary term when something serious is happening and there is humor?
2 answers
http://www.buzzle.com/articles/glossary-of-literary-terms.html#I
Or maybe Irony.
Or maybe Irony.