During the season finale of DC's Legends of Tomorrow, the legends had to travel back to 1916 France. However, there was one catch. Their team was already there as they were conducting a mission in the past. They feared breaking the first rule of time travel, which isn't "Don't talk about time travel." Back to the Future fans knows the first rule is to never interact with one's self in an another time.
Sadly, the group did run into themselves. At first, they mistook the other legends as imposters and traded blows. After things settled down, the legends confronted their former selves and surprisingly didn't get along. However, they were able to team up and send the legends back to current day.
The episode ended with the group trying to escape to a vacation in Aruba but crash-landed in 2017 Los Angeles that unexpectedly had dinosaurs roaming the city.