In levels where Toad is trapped you need to save him. Depending on where the time counter is when you end the level decides on which Mushroom House you get.
Gold Mushroom House - 7, 8 or 9
Green Mushroom House - 0, 1, 2 or 3.
Red Mushroom House - 4, 5 or 6
Once you beat the last castle in World 8 a new save feature will unlocked. This feature allows you to save your game anywhere. Where ‘Quick Save’ once was will be this new option