In Batman #107 (Feb 1957), Dick Grayson (Robin) accidentally is exposed to a gas that ages him to adulthood. Yep, it turns out that Superman was too busy to analyze a lead-lined device he found in space, so he left it with Batman, and poor Robin took a blast of space gas in the face. Hate when that happens.
Anyway, it results in a cool little story where Robin re-trains his body and suits up as Batman’s new partner, Owlman. I thought it was kind of funny because of the obvious comparison to Watchmen.