Regular Show ended with a three-part finale that was as meta, bizarre, and emotional as one would have expected. One of the best Cartoon Network shows of all time, Regular Show concluded its eighth and final season with a battle for the fate of existence itself. After trying to avoid fighting his brother, Pops had no choice but to face Anti-Pops in a battle that had already happened billions of times. This time, however, Mordecai and Rigbys intervention made sure that the universe was not going to be rebooted.

https://screenrant.com/regular-show-season-8-ending-explained/