Quest A: Look for a Luxo Ball (box). Follow the sidewalk to find Alyx's doll sitting on a bench. If you happen to lose this doll by accident, you can jump through the portal below the Thanks Box. When you die, you'll see another doll come out of the tube.

Quest B: Go to the pool. Look along the walls until you see a big hole. Below it should be a yellow button. After touching the button, Bunger Jr will spawn at the jumping board.

Quest C: Take the downstairs inside and jump into the green tube.