How Markiplier and ‘Iron Lung’ Turned the Box Office Upside Down: ‘I Thought It Would Come Out in 200 Theaters’

As the holiday box office period was winding down, it was looking like movie theaters were facing another deep multi-week slump. But this past weekend, they were able to stem the tide with the help of an unlikely debut filmmaker: Mark “Markiplier” Fischbach.

After 13 years building a YouTube fanbase of 38 million subscribers with his popular “Let’s Play” videos — including a “Five Nights at Freddy’s” series that launched that horror game’s popularity — as well as a variety of creative projects...