Comic relief

Comic relief usually means a releasing of emotional or other tension resulting from a comic episode interposed in the midst of serious or tragic elements in a drama. 
It's used for comic relief will usually comment on the absurdity of the hero's situation and make comments that would be inappropriate for a character who is to be taken seriously. Other characters may use comic relief as a means to irritate others or keep themselves confident.
I remeber a funny scene in:

The Exorcist