In the Night Kitchen to a group of kindergarteners who are not going to miss the subtle fact that Mickey is as naked as Michealangelo's David. So, what do you do? You can try to ignore it, or give them a lecture, but my advice is to let them laugh. For exactly one minute. Time it.
Tell your class that they get one minute to laugh, say the funny word(s), make the jokes, whatever. Make a big deal (espcially if you have little kids) of timing it. Then give them their minute. When it is done, make it clear that the silliness should be out of their systems and you expect them to behave appropriately.
I have used this technique with great success. Occasionally, I have had to give a second minute. However, that one usually happens at recess time.