The happy-face sad-face tattoo represents the principle of laughing now and crying later. A person who gets this tattoo can believe that it's best to live life to the fullest now and deal with the consequences later, according to Bullseye Tattoos.
The happy and sad faces of the tattoo can also represent comedy and tragedy. The faces are ancient Greek theater masks; they are said to be the faces of Melpomene and Thalia, who are the muses of comedy and tragedy. The masks were used to convey the feelings the actors on stage were trying to portray. They can also indicate that the wearer of the tattoo is very passionate.