The Swedish internet star, who has more than 47 million subscribers to his humorous YouTube video channel, surprised and horrified some of his fans Tuesday when he tweeted that he and fellow blogger Sean William McLoughlin had joined the terror group.
PewDiePie, whose real name is Felix Kjellberg, had been protesting at the social network's "annoying" verified accounts system which can generate automatic notifications on smartphones.
"Me and JackSepticEye have joined Isis," he tweeted, "Which is why we both got unverified."
But the exchange went down badly with some of the 26-year-old Swedish blogger's fans, who first shot to fame for his gaming videos.
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"That's not something to joke about," one reprimanded him. "ISIS isn't something to take lightly. It's serious. I love Pewds but I don't like this."
Then Twitter suspended his account -- which at the time also carried a sexually graphic profile photo -- to a further howl of protest from a group of his fans.
The account was later unblocked with PewDiePie tweeting, "I'm toally fine guys, I am feeling very good today and it's actually so heartwarming to see so many people care about me."
In a new video blog on his YouTube channel he said that he made the ISIS joke to ridicule a tweet from "an obviously fake website called Sky News (a fake account with the same name as the British broadcaster) which had claimed that 'Popular YouTuber Pewdiepie (was) unverified due to suspected relations with ISIS'".
Pewdiepie said that "it would have taken people half a second" to check to see if the account was real, but most didn't and "so people started believing that I had joined ISIS...