Holiday Whodunnit 2021 Event

 or Christmas 2021 Event or Winter 2021 Event is the 6th multi-event of 2021, the 18th multi-event overall and the 10th Christmas Event. It was released on December 8, 2021, one week after the conclusion of Northward Bound 2021 Event and ended on January 12, 2022.

Similar to previous multi-events, it was divided into 4 acts:


 * Act 1: December 8, 2021 - January 12, 2022
 * Act 2: December 17, 2021 - January 12, 2022
 * Act 3: December 26, 2021 - January 12, 2022
 * Act 4: January 4, 2022 - January 12, 2022

"It's a regular old Ho! Ho! How? Christmas is on the brink of ruin... Santa has been beaten into a coma! Will he recover in time to deliver presents? Does he even remember who's been naughty or nice? And will anyone bother to solve this case? Permanent nice list members Lisa and Marge are tracking down the bah-humbug slugger himself, all with the help of Santa's old friend Herb Tannenbaum. Cause you can't spell Merry Christmas without crime!"

- event's description.

Daily Challenges
During the event, new challenges were added. These additions replaced the usual Daily Challenges.

Trivia

 * Most of the event's theme and new content on Season 25, Episode 8 "White Christmas Blues" and Season 31, Episode 10 "Bobby, It's Cold Outside".