A futurenaut is someone who is given a mission by someone from the future. They have become a staple cliche in many science fictional. The term was coined by Disney's Wizards of Waverly Place in the episode "Future Harper", but has been present in many dramas and comedies long before. This term should not be confused with the person who actually travels back in time to relay such a mission.
Examples of Futurenauts include:
Ebenezer Scrooge in The Christmas Carol
Sarah Connor from The Terminator series.
Goku from the Dragonball Z series.
Bill and Ted in Bill and Ted's Excellent Adventure.
A number of people in the Doctor Who series.