Themes
Wrinkles should merely indicate where smiles have been.
— Mark Twain

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker wishes that the lines of age would simply record where smiling has happened. Wrinkles become a map of past cheerfulness rather than a sign of decline. It is a gently witty hope that a life of laughter should leave a face marked by pleasure.
Context reviewed