Games in which actual developers of the game address the player directly, to talk about the game, inside the game
I thought about this while I was building my GotY 2019 list and got to Anodyne 2. A combination of Breaking the Fourth Wall and Developer Cameo, this is when someone from the development team of the game honestly talks about the game itself, inside of the game. Not in a developer's commentary mode or anything, just showing up and saying "Hi" when you were playing the game normally.
Maybe this should be a concept page or something, I don't know, I can't be bothered figuring out the taxonomy for that sort of business. I'll just keep adding to this list the more examples I find, the same way I do my other lists.