Over the past few years, Let's Play videos - where avid fans watch other people play video games on the internet - have exploded to new levels of popularity, with both YouTube and live streaming platform Twitch capitalizing on the craze.

But it's not just YouTube and Twitch that are making money from Let's Play videos: the content creators themselves are also raking in the cash. PewDiePie, for example, managed to make around 63.7 million Swedish Krona (around US$7.5 million) from his Let's Play videos in the past year, up from around US$4 million in the year prior.

PewDiePie, a 24-year-old Swedish man by the name of Felix Kjellberg, currently holds the record for the most YouTube subscribers at 37.7 million. Kjellberg has held the record since late 2013, and considering he has a 15 million subscriber lead on the second place holder (Chilean channel HolaSoyGerman), he will likely hold this record for years to come.

Kjellberg works with and donates a lot of his YouTube earnings to charity, saying in a Reddit AMA last year that he has "spent far more money on charities than anything I've ever spent for myself. Which I am proud to say at least." Fans of PewDiePie have also contributed to charity in a meaningful way, raising a combined $1 million in June 2014.

It's not just Let's Play videos that PewDiePie is working on though: Kjellberg has a book in the works called This Book Loves You, which is set to be released in October, alongside a video game called PewDiePie: Legend of the Brofist that will launch "this summer" on iOS and Android.