Can a token created by a copy effect be returned to the battlefield from the graveyard?

Tokens are not cards, and the rules have a specific cleanup process for them. Under CR 704.5d, a token in any zone other than the battlefield (or the stack, while it's resolving) is put into the graveyard as a state-based action — but then immediately ceases to exist. This means the token never actually 'lives' in the graveyard long enough to be targeted by a spell or ability.

This applies equally to tokens created by copy effects (e.g., Clone copying a creature, or Cackling Counterpart creating a token copy). The fact that the token is a copy of something does not grant it any special persistence. Once it leaves the battlefield, CR 110.5g dictates it ceases to exist the next time state-based actions are checked.

Because the token no longer exists in the graveyard, any spell or ability that says 'return target creature card from your graveyard to the battlefield' cannot legally target it. There is no object there to target, even if the token was a copy of a legendary creature or a powerful permanent.

Concrete example: You control a token copy of Grave Titan created by Followed Footsteps. It dies in combat and goes to your graveyard. You try to cast Unearth targeting it. This is illegal — the token ceased to exist as soon as it reached the graveyard, so there is no valid target for Unearth.

Note: A non-token creature that entered as a copy (e.g., a Clone that copied a creature) is a card and does remain in the graveyard normally, so it can be reanimated. The key distinction is token vs. non-token permanent.