You're Joking

You're Joking is an achievement in Halo: The Master Chief Collection. It is unlocked by completing the Halo 4 campaign on Legendary in under 3 hours.

The 3 hour time limit is calculated as the sum of the player's best times on each level on Legendary on either solo or co-op; players can view their best times on their Halo Waypoint service record. As a guide, players should roughly aim for the par times as they total 2:40.

Trivia
The achievement is named for Halo speedrunner ProAceJOKER, who held the world record speedrun for Halo 4 on Legendary in 2014.