They help you get up onto the leaderboards, but you need 2 decent players to trigger them.
Bo Peep and Wheezy balloon pop -- each player works on clearing the 5ish balloons on each cloud on their side, have both players hit the last balloon on their cloud at the same time to switch the room to rainbow which drops tons of 2000 pt rainbow balloons
Army Men plate break -- on the mountain ridge near the top, 2000 pt plates are thrown up in the air then fall back down. If both players hit the plate on their side, the middle mountain will lower revealing a tank that shoots 4000 pt plates. Also 3-4 2000pt plates are now tossed up on each side instead of just 1.
Buzz's Ring Toss -- put a ring on every alien in the center spaceship before they respawn and the spaceship will blast off revealing a box. The box will periodically open with increasing pt values. Toss in as many rings as you can while the box is open.