Iron Lung was a flop with Rotten Tomatoes critics — but its $21M box office debut is a huge win for independent horror

Iron Lung has shocked viewers with a massive $21.5M opening weekend in theaters, following close behind Sam Raimi's new horror movie, Send Help, which has a much bigger budget and star power.

While I'm delighted to see two horror movies performing well, it's particularly notable that YouTuber Markiplier (real name Mark Fischbach) has achieved such incredible success, with huge box-office takings despite a comparatively small $3M budget.

Iron Lung was self-financed by Fischbach, who also directed and starred in the movie, so it's very much a passion project for him. It's based on the video game of the same name by David Szymanski, an independent game developer, who worked closely with Fischbach on the movie.