During the meeting between the Golden Age Superman and Batman, Superman tries to convince Batman to join them, explaining to him in a completely non-threating and friendly way why he should help them, how everyone's life would be better if he did so, as everyone on Earth-1 is darker and more twisted than they are on Earth-2. Bruce's answer? "And what about Dick Grayson?" Superman is completely lost for words, proving that Dick Grayson truly is The Heart of the DC Universe.
Crosses over with Moment Of Awesome, but Bart Allen vs. Superboy Prime. When Jay Garrick falters due to his age and Wally West leaves to say goodbye to his family (itself a Heartwarming moment) Prime berates Bart for being stupid, a child, alone, etc. even as Kid Flash drags him into the Speed Force. Bart starts to falter even as he declares "I'm not stupid." At that point, his grandfather, Barry Allen, who had been dead about 20 real-time years, emerges from the Speed Force, grabs Prime in a choke hold and tells him he isn't alone, either.
When Bruce goes on his self-discovery quest, as he done before, only it'll be different this time he's not going to be alone because his two adopted sons Dick and Tim are coming with.
In a meta-sense, the reasoning behind Nightwing's survival - DC Editorial originally wanted to kill off the character in the events of the story, because his status as The Heart of the DCU would send shockwaves throughout the entire company. Geoff Johns outright refused to write it.