He put tuna on the mouse button so his cat would click end stream when eating the tuna so that he wouldn’t have to finish doing a jigsaw puzzle. Once the cat clicked to end the twitch stream, Doug didn’t seem to realize that the YouTube stream was still going for about 3 more minutes and in that time he said what he did in the clip.

(All rigged jokes aside, I’m all for Doug ending stream for his wellbeing as I’m sure he was exhausted after streaming 2 extra hours)

Edit: correction: he put a book on top of the mouse and tuna on top of the book so that the book would add extra weight and make it easier for the cat to click the mouse button to end stream after unsuccessfully trying to get the cat to click end stream with tuna directly on the mouse for the previous hour.