They didn't hide it from the audience. They did the reveal in "Herstory of Dance." The episode starts off with Pierce saying "And then in the season finale they reveal the whole thing was a dream."

Empire - Vader says he's Luke's father, but might be lying

Empire - Vader says he's Luke's father, but might be lying

One other thing to note about how great his episode is structured, the catalyzer on the compression coil is what broke.

One other thing to note about how great his episode is structured, the catalyzer on the compression coil is what broke.

I wonder how many people will actually get that reference.

He knows Amy, Rory, and River were summoned by him to Lake Silencio at the same time he was, at the date of his death and that the event is a fixed point. He has to summon them again or it completely screws up the timeline and that fixed point.

Justice League is good, but if you are going to look into Superman: The Animated Series, (and there are a few crossovers to Batman: TAS) it should probably be done first since both B:TAS and S:TAS flow into Justice League canon, especially encounters with Darkseid