In commercials, you always see people laughing. This is done for a reason: the more a person smiles, the more atractive the person becomes, and the more attractive the product becomes that is presented in the commercial.
Smiling people sell better, thats an old saying in the creation of commercials. The faces on the covers on the magazines in the kiosks look with a laughing face at the costumers, trying to get their attention. A human face plus a laugh is an old sales trick. Even the classical music industry uses this rule. On cd covers of classical music cd’s and dvd’s we often see a singer or conductor smiling.