Superhero costumes have a slight tendency to be tight, revealing the shapes of almost every body part they cover. Except, thank God, for Hulk's pants.
This implies that superheroes have found a way to get rid of their civilian clothes before gearing up, otherwise some six- or eight-packs would be hidden by the super-suit molding a winter jacket, as well as other (mainly female) body parts writers judge worthy of attention. From where I stand, we can distinguish between several categories:
- "I have super-speed, so one can assume I just drop my civilian clothes somewhere": Flash, Superman, Quicksilver...
- "I don't have super-speed or any superpowers for that matter, but I manage": Daredevil, Green Arrow...
- "I'm kind of a public figure so I can gear up without worrying too much about such things": Wonder Woman, Aquaman, Captain America, Iron Man, Fantastic Four...
- "I don't care, I'm a shapeshifter": Martian Manhunter, Mystique...
- "Shut up, it's magic": Zatanna, Doctor Strange...
- "I'm Batman"
And then there are Green Lanterns1. Green Lanterns have great flight speed, but no speed to gear up and ditch their blue jeans the way Superman could. In fact, in most cases the uniform just appears to somehow replace the clothes, as depicted in the cover below:
This is supported by the fact that when the suits rips, what is often shown is skin, like here:
Though when it's needed for view angle reasons, Jessica gets her clothes back:
These examples are quite recent though, and Green Lanterns have been around for a while.
Was it ever explained, in comics or elsewhere, where the civilian clothes go when their suit is on, or if they actually stay there, why the green uniform fits the abs despite leather jackets? (apart for the obvious out-of-universe reasons that breasts and abs sell more issues)
1 Actually, I reckon every color of Lantern uniform behaves this way, but I'll just say with Green Lanterns for clarity. If the answer comes from another shade of the emotional spectrum, it's not a problem though!