On delfino square when u go round the first thing near the sea, there will be two crates. ram into them then and go around them. there should be a passage there.
in bowser castle when u go around that moving that circle go past the door and keep going till u find another door and go through and you'll be on red carpet.
on mushroom bridge after the start where you go trough a tunnel when u come out keep going forward there will be a dirt path and go up it an down again.