For those who are interested, Drake was playing on his PS4 and Ninja was on his favoured PC.
One wrote on Twitter: "So I'm watching @Ninja play Fortnite with Drake".
Scott, who recently welcomed a baby with reality TV star Kylie Jenner, also let his fans know he was involved by tweeting a screenshot from the game.
The stream is about to reach 600,000 viewers - that's over four times the high view count for Overwatch League tonight.
Ninja himself has over 3 million followers and 160,000 paid subscribers, whilst earning an estimated income of several hundred thousand dollars a month.
The popularity of the tie-up is a PR victory for Fortnite-maker Epic ahead of its launch of a version of the game on iOS and Android mobile devices. The game is a little bit like Minecraft in that a lot of the game-play involves breaking down and collecting resources to create fortifications against a zombie horde. Later on, Travis Scott and JuJu Smith-Schuster hopped on for squads.
Like Drake, Smith-Schuster is an avid gamer and that he revealed during the stream that he has played the game on many nights in the studio. It's where gamers from all over the world can watch or play against complete strangers. Games of this kind have skyrocketed in popularity past year thanks to another immensely popular game, PlayerUnknown's Battlegrounds. "Drake said he had to pack for a flight tomorrow so he's out".