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

A close up of Markiplier in Iron Lung, looking scared.

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.