Note: glitch happen when I was on 1-1 and playing hard mode.
First get the star power up in 1-1 and run to the goal and get to the goal at the top but jump over it so Mario is off screen. If you still have the star power up the music should change back and the game looks like its frozen because the only thing happening is the music but if you hit start to pause and hit start again to unpause the game, the game will start to act normal again. Since I was playing hard more it should work in normal mode too.
First get the star power up in 1-1 and run to the goal and get to the goal at the top but jump over it so Mario is off screen. If you still have the star power up the music should change back and the game looks like its frozen because the only thing happening is the music but if you hit start to pause and hit start again to unpause the game, the game will start to act normal again. Since I was playing hard more it should work in normal mode too.