Why would Two-Bit think that Dally, Johnny, and Pony were heroes all along, before they saved the kids?
I stared at the newspaper. On the front page of the second section was the headline: JUVENILE DELINQUENTS TURN HEROES. "What I like is the 'turn' bit," Two-Bit said, cleaning the egg up off the floor. "Y'all were heroes from the beginning. You just didn't 'turn' all of a sudden."
Two-Bit's comment highlights one of the themes of the novel The Outsiders. Throughout the novel the reader sees that there is a polarity that exists between characters' outside appearances and their inner characters. The world looks at Ponyboy, Johnny, Dally, Two-bit, etc. as nothing but a bunch of Greaser juvenile delinquents. They see gang members with too much free time on their hands who are only looking for trouble.
Two-Bit's comment highlights what he has always known about the other three: that their strength of character was always heroic. If that character trait wasn't ever there in the first place, those three boys would NOT have risked their lives to save the children in the church. Two-Bit knows that both Ponyboy and Johnny are truly good-hearted people. Even at the end of the novel when Two-Bit thinks Pony is hardening because of the deaths, he is reminded of Pony's true character when Pony starts to pick up the glass so nobody gets a flat tire. In Two-Bit's opinion, those boys were always heroes based on their strength of character, not because of a heroic deed.