Reincarnation is the belief that a soul when it dies is given another form to live in a constant cycle of birth and death. How that applies depends on the belief system that teaches reincarnation, as one person's belief in reincarnation may be that the person appears in a form similar to the last form, though distinctly different (such as a human being reincarnated as another human), while another person's belief in reincarnation may be that the person appears in a form that's entirely different from the previous form (such as a human being reincarnated as an animal).
Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Traveler discovered through further exploration of "The Blue Plague timeline" that the Smurfs that died in that tragedy would be reincarnated as a new generation of Smurfs that Brainy and his female counterpart would be in charge of years in the future. However, reincarnation does not appear in the series' main timeline among Smurfs, humans, or other living beings, as there is a defined destination for all beings to pass on to when they leave the mortal life.
LD Stories
Within The Light and Dark Series, Falla is a person who believes in the possibility of reincarnation. As she claims at one point, she believes she was once a bird in another life since she has a migratory nature, but she also wants a homestead that she can return to year after year.
The Smurfs are open to the idea that Mother Nature and Father Time control who is reincarnated into what creature upon their death and new life, but some Smurfs argue about how true this may be. No one is quite sure (no matter what Brainy claims).