At the time, "second screen" was the term I heard used for those types of experience. The only prominent example I can think of these days is kahoot, which is only sort of the same idea.
Ah yes, I'd forgotten about the phrase "second screen". It was going to be big thing until people realized that no one wanted to look at 2 screens at once.
That's not my experience. There's a constant background hum of "what else have I seen him/her in" in my house.
Not so much "lets all talk about this in realtime!" I admit, but there seems to be a subset of people who use Twitter/Reddit like that when watching politics or sports.
I'm one of them, for example eurovision or euro'20 in a few weeks. Memes and stuff it's literally better than watching it. It just become a base to make memes of