In World 2-4, just past the two Piranha Plants (after the mid-level point) you will come to a staircase with a turtle coming down it. Jump on the turtle just as it is about to go off the third stair (third from the bottom). If done correctly, Mario will continue to jump on the turtle and earn up to 99 lives. If you miss the turtle, go back towards the left and return to the staircase and the turtle will respawn. This is a reference to the original Super Mario Bros., in which you could do the same trick to get unlimited lives.
Go to World 7-4 as Mini Mario. Go through the stage while staying on the left side. You will eventually see a "?" box and a ledge. Jump on the box then to the ledge. Jump off the ledge, making sure to stay against the wall and you will reach a platform with a pipe leading to a red flagpole. You will unlock a 1-Up mushroom house to the north of World 7-4, which never disappears. You can continue to get 1-Ups until you reach your maximum of 99.
In World 7-5, throw a Koopa shell in-between the two Bullet Bill cannons to get an extra life every four seconds.
