i believe that bowser begin to take over the mushroom kingdom and that they did send Mario and Luigi but i think that Mario and Luigi ARE human and that their parent's found the mushroom kingdom somehow and thought that it would be a nice place to live. i also think that bowser lied dormant for years and then when his troop's were Strong enough he begin a war, of course the toad's are not very strong and so that would mean that there was a another hero before Mario. but something happened (he died or thought that the danger was gone) and disappeared from the mushroom kingdom. I'm going to skip a few years to when they were grow up, to what we do know for sure is that Mario and Luigi found a pipe and went inside and come out in some transport pipe bypass thing, where they fought monster's, after which toad's come to help and the rest run away, here we enter super Mario bros where the toad's ask these "great warrior's" to rescue their princess which has been kidnapped by a huge "koopa troopa" name bowser, Luigi probable was in a "well we would love to but" state of mind but Mario, a born hero was all for it. when the princess was back and safe, Mario was give a castle and Luigi was given a house somewhere in the mushroom kingdom as seen in paper Mario: the thousand year door when Mario was visiting Luigi that he had his mail sent to Luigi's house, but anyway, after Mario gets a castle the toads need him to rescue another princess named Daisy enter "Mario land". after Mario comes back to his castle, he finds that a new fiend has take over his castle and hidden his 6 golden coins (like keys, his only way into the castle) with evil guards. the evil person's name? Wario. super Mario 64 is simple. peach gets kidnapped. IN HER OWN CASTLE!. so you have to save her. super Mario sunshine is when Mario gets framed my bowser Jr the 8TH! koopa kid and bowser favorite (bowser named him after himself, i mean come on!) i know nothing about super Mario rpg or paper Mario (the 1st one,not ttyd).
if you can help me anyway you know how please do. thank you