Why is "Junior" in Breaking Bad all of a sudden now called Flynn? I thought he was dubbed Junior as he is also Walter White (Jr.). Is Flynn a middle name or second given name?
Walter Jr. starts calling himself "Flynn" in the Season 2 episode "Down". He does it to distance himself from his father.
He grows apart from Walt due to his father's absences and bizarre behavior, being taught to drive by his friends and wanting to be called "Flynn."
From a 2009 interview with RJ Mitte (Walter Jr.):
Q: Walter Jr. gives himself a nickname this season. Any idea where "Flynn" came from?*
A: I know it was an old movie star -- Errol Flynn. It took me a while to figure out where it came from though. I asked Vince, "Flynn? Out of all the nicknames?" And he's like "Well, that's why I picked it."
Walter Jr decided that he didn't want to be called Walter White Jr as that's his dad's name and isn't cool. He was a teacher at the school his son goes to so I guess there is some pressure there.
There was never any reference to where it came from or why he chose it, I guess it's just different to Walter.