Things You'll Need
Instructions
Firt, in order to gain infinite lives in Super Mario Bros. Wii, you will need to get to World 2-3. Do this simply by playing through the levels leading up to this world.
In world 2-3, find the staircase in the middle of the level that is located just past two Piranha Plants.
You should see a turtle walking down these stairs. Wait until the turtle is on the third stair from the bottom. When the turtle is just about to step off of this stair (but is not yet off), jump on the turtle.
When done correctly, Mario will continue to jump up and down on the turtle as you gain up to 99 free lives.
If you don't time it right, you can simply go back in the level until the staircase is well out of sight and then try it again.