Smile

You may be looking for the TV story.

A smile was a facial expression that involved the turning up of one's lips, sometimes showing teeth, primarily serving as a sign of happiness.

Shortly following his regeneration, the Tenth Doctor made Rose Tyler smile with a quip that, being familiar with her mother, nut loaf would be a more appropriate choice of Christmas dinner for the elder Tyler to prepare. (TV: The Christmas Invasion)

Overseeing the operation of a hologram of Joseph Serf, Plark instructed his fellow Skullions to repeatedly make him smile as he conversed with Sarah Jane Smith. However, they made the mistake of giving him a "sexy smile", which Plark ordered amended to "thoughtful smile". (TV: The Man Who Never Was)