An all-new episode of CBS' "How I Met Your Mother" promises to be hilarious as Barney may have actually come up with his worst idea, ever.

In a preview of the upcoming episode, which is called "Rehearsal Dinner," Barney comes up with a laser tag rehearsal dinner idea and Ted dresses up as Liberace.

According to Hollywood Hills, Barney will become fixated on having his rehearsal dinner at a laser tag arena, much to Robin's dismay. Meanwhile, Ted aggravates Lilly when he ends up coming through on a promise.

Also featured in the show, are lots of quotes and jokes about Canada which are designed more or less to taunt Robin.

Guest stars on the show include Wayne Brady as James, Alan Thicke as Himself, Patrick Hancock as Security Guard, Lawrence Larsen as Dr. Frederick Banting and Victoria Boa as Louise Poirier.

TV Line revealed more spoilers in an episode later on in the season.

"There's an episode coming up that's ... mostly in flashback and mostly set in China," EP Craig Thomas shares. And if you're all "Huh?" - and I reckon you are - he adds, "It will make sense once you see it." And there'll be other episodes like it, including the "rhyming" half-hour airing Monday. "There's a lot of crazy time machine, structural jumpiness coming up that I think people will enjoy," Thomas says.

"How I Met Your Mother" S9E12 is set to air on Monday, Dec. 2 at 8 p..m EST on CBS.

Watch previews of the episode below: