Have you ever found yourself in an uncomfortable situation and behaved differently than you would otherwise. Some people when facing a stressful situation behave in a silly, almost giddy fashion - clowning around. (Remember when you could barely speak when you were around that person in junior high or high school that you always had a crush on?) Children can react in a similar fashion. One way to look at this behavior is letting off some excess steam. While the release of tension can be beneficial, the clowning behavior can escalate and become, at best quite tiresome, and at worst something that impedes your child from making connections that are meaningful if they hide behind the clown all of the time.
Pay attention to me, only me, and right now!
One reason that children may cut up is that they are reacting to a situation that makes them uncomfortable and do not know how to behave in the situation. This often is the case when a friend or relative is over and the parents are engaged with the other adult and expecting the child to entertain themselves. The child does not want to miss out on the fun, so they come up with ways to gain attention and do so in a cute, funny or charming manner.
When your child is acting silly in an attempt to get your attention, you should address them immediately. Saying something like, "I know that you want to spend time with me. I want to spend time with you as well. However, Aunt Kathy is here and we want to visit. When she goes home later, I will spend some time with you. Please go read your book, play with your sister, or watch your movie and I promise to spend some time just the two of us just as soon as Aunt Kathy needs to leave." This response shows your child that you care about him, that you are aware of his needs, gives an assurance that you will spend time with them (and make sure to do so), and gives them a view of you as an autonomous being.
The family clown
If your child feels that they receive the most positive attention while being silly, this may become a habit both at home and at school. While parents usually put up with more silliness than a teacher does, for some parents, this behavior is quite troublesome. Teachers cannot have 28 class clowns and must curb the silliness. If acting silly has become your child's primary mode of interacting, there is a good degree of possibility that the behavior is a habit and that they will get into some trouble at school for cutting up all of the time.
Don't look over there - look here!
When there is tension in the family, sometimes children will act silly in order to distract their parents (or other family members) in an attempt to help cheer them up. This behavior is quite common in families that are facing separation, divorce, illness, financial hardship, the death of a loved one, etc. In an attempt to distract attention away from stressful or emotionally difficult situations, a child (or adult) may feel the need to launch their own stand-up act. When your child is in this mode, it is important to assure them that you appreciate their support and desire to make you happy and forget your stress, but that sometimes life is stressful and that this is OK.