Easter egg:
For this, you will need a Four-Score adapter to allow four controllers to be controlled simultaneously. When you beat a random hockey battle, when you win, press A + B + Start on Controller 3 during the victory sequence. This will repeat the animation sequence.
Sound test:
At the title screen, after "Push Start" appears, press A, Up, B, A, Right, B, A, Down, B, A, Left and B. If done right, the sound test should appear.