Tattoo

A tattoo is a form of body modification that made by inserting indelible ink into the dermis layer of the skin to change the pigment. In mainstream Smurfs media, Hefty is the only known Smurf character who has a tattoo mark, a heart that appears on either or both upper arms.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Hefty's heart mark on his right upper arm is actually a birthmark while the one on his left upper arm is a tattoo. There is also Swimmer Smurf who has a blue fish tattoo on both his upper arms. It is believed that Painter is responsible for the application of both Smurfs' tattoos. In an alternate timeline where Empath was forced to return to Psychelia a year after his 150th birthday, Smurfette also began to wear a heart tattoo on her arms.

Psyches have tattoos in the form of their designation code branded on the back of their heads when they first emerge from their gestation chambers to begin their training. Empath was also branded in the same fashion, which makes him feel rather embarrassed to show his bald head in public during his later years in Psychelia. Strangely, while Papa Smurf has developed a tattoo remover formula for Empath to use regarding his designation code imprint, Empath refuses to use it on himself.

In the Mirror Universe, Hefty has a skull-and-crossbones mark on his upper arms and Wild has stylized animalistic markings on his face.

Second Smurfette series
In The Second Smurfette series, Broad Smurfette is a female Smurf character who wears a tattoo mark in the form of a gray star.

Hero: The Guardian Smurf stories
Besides Hefty, Hero in the HERO: The Guardian Smurf story series also wears a tattoo, a white shield on his right arm. His Grey Smurf counterpart also wears a shield tattoo on his right arm. When he is transformed into Dark Hero his tattoo turns into a sword.

Sympath: Smurf No. 1 stories
The main character of the SYMPATH: Smurf No. 1 story series had a yellow star imprinted on his forehead when he was abducted and raised among the Cognites. Papa Smurf, however, would come up with a formula that could safely remove this mark from Sympath's forehead.