Possible Plot Twists

Fendor faked his own death (as everyone suspects) but so did Meredith. Meredith then killed Fendor for real, using Mac's knife, during the macarena, and she is the one who has been moving the statues.

All of the characters except Benny are animatronic robots that Benny created in the alien lab, but due to the trauma on New Year's Eve, he's suppressed that knowledge. He will regain his memory, and then in a climactic final scene will discover that he is also a robot, created by the aliens before they left Earth, and Sherene has known all along.

The characters are all dead and in Hell; Benny is Satan.

The characters are all dead and in Heaven; Mac is God.

The characters are all dead; Benny is God, Mac is Satan, and the two are vying for control of the others through the visions.

Meredith and Mac are working together to drive Benny insane, so they can split the lottery winnings between them; everyone but Benny knows that Meredith is still alive, but don't mention it to avoid enraging him again.

Sherene and Mac are lovers, and only pretending to hate each other to keep Meredith from suspecting.

Benny and Mac are lovers, and only pretending to hate each other to keep Sherene from suspecting.

Sherene has a key to the Circular Room, and has been slipping in at night and planting the “alien messages” to manipulate the others.

Fendor was not killed by the poison, and regained consciousness during the macarena. He is the one that lit the fire in the abbey, and used the distraction to steal Meredith's papers.

Anyone entering the Circular Room is transported forward in time by one day (alien technology). This is how Meredith could reappear in the dining room after the macarena; Mac was not involved in any way.