'Terrifier 3' Star Says He's Shocked Indie Film Won Weekend Over 'Joker 2'

'Tis the season for clowns ... and, while "Joker: Folie à Deux" was supposed to reign supreme as Clown Prince of Cinema, a more horrifying harlequin is crushing the box office.

"Terrifier 3" -- a low-budget gory horror flick following a serial killer dressed as a clown -- hit the box office this past week and has soared past 'Joker 2' already ... raking in $18 million while 'Joker 2' made just $7 million this weekend.

We sat down with David Howard Thornton -- who played Art the Clown in all three 'Terrifer' films -- and, he tells us he's stunned ... calling this a David and Goliath matchup of a small indie film against a massive studio project.

DHT chalks up the success to two things -- the 'Terrifier' series' rabid fan base, and staying true to the soul of the flicks.

David says the film was approached by studios with financing offers, but the moneymen wanted to change the movies in a way the creative team felt uncomfortable with ... so, they turned the offers down.

David says he thinks a big problem with movie theaters is studios aren't making films people need to watch in big groups ... so, there is less incentive to go out and watch a movie. He says "Terrifier 3" is the best when watched in a collective -- a major plus in their column.

BTW ... David's got plenty to say about the 'Joker' films -- watch to the end to hear why he's so shocked the sequel is bombing.

As you may know ... "Joker: Folie à Deux" had a bad opening week at the box office, and seems poised to lose a lot of money. Sources have told outlets like Variety the flick needs to make $450 million to break even. To date, it's only made around $215 million worldwide.

"Joker: Folie à Deux" has just a 33% on Rotten Tomatoes -- and an abysmal score on the review aggregator.