Dean and Sam are headed to crazytown in tonight's "Supernatural" season 11 episode. Titled "Just My Imagination," the Winchester brothers are off to their most insane mission yet, which is looking for an imaginary friend murderer.

The hunters will be on the lookout for the creature that preys upon children's friends from fantasy land. Helping the duo is Sam's childhood imaginary pal Sully, whom Dean can also see. Needless to say, executing the investigation without looking like total crazies is impossible so the duo device a plan.

In a sneak peek at the upcoming "Supernatural" season 11 episode, they introduce themselves as trauma counselors for kids to a mom of a young girl that claims her half-man half-unicorn friend named Sparkle was killed.

Unbeknownst to her unsuspecting mother, an imaginary killer that slays imaginary friends really is on the loose but she thinks that the death of the "manicorn" as Dean refers to the youngster's dead fictional buddy was all a product of her daughter's "active imagination."

Tonight's "Supernatural" season 11 will be full of flashbacks to Sam's childhood that will help explain why Sully suddenly popped up and even shows himself to his creator's ever-skeptical brother. Overall, the episode should be a fun, memorable filler.

Majority of the episodes of the season have been building up the Darkness reveal. While it remains to be seen whether or not "Just My Imagination," especially the flashbacks in it, will shed light on Amara's existence remains to be seen. Nonetheless, it is expected to make for a great episode.

Speaking of which, show's leads Jensen Ackles and Jared Padalecki opened up about their characters' battle against the Darkness, who was revealed to be God's sister.

It isn't clear if the big man will help the brothers contain the evil entity but one thing's for sure – Sam and Dean won't stop until they managed to do just that. "They're going to do it come hell or high water, with God's help or with God trying to stop them," Padalecki explained to Entertainment Weekly.

"Supernatural" season 11 episode 8 "Just My Imagination" airs tonight Dec. 2 at 9 p.m. ET on The CW.