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-So, were you born with superpowers or exposed to sth?
-A couple weeks ago (2 weeks ago?) I got caught up in chemical fire and here I am.
It's common to the archetype. It happens often?
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Madhulk-A couple weeks ago (2 weeks ago?)
Roughly, but not necessarily exactly.
Madhulk
It's common to the archetype. It happens often?

This is not a set phrase with an idiomatic meaning (not as far as I know, anyway). It appears to mean just what it says, and no more.

An "archetype" is an original or ideal example of something, on which other similar things are modelled. He's saying that "it" is a common feature of that archetype. What "something" and "it" refer to, I can't tell.
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Thanks, Mr Wordy!