Take a large box and cut openings in the front and sides, and a hole at the bottom for your legs. Support the box by attaching it to a backpack that you wear with the straps hidden under your clothes. Glue a small box to the front with a joystick, buttons and coin slot, add a hanging crane made out of wire, and decorate the whole box with paint. Wear whatever animal costume you'd like, climb inside the box, throw in some small stuffed animals, and attach the crane to your head.
Aquarium:
Turn a large cardboard box upside down and cut holes for your arms and head. Cut a square piece out of the front, paint the box silver or black, and glue in a piece of clear blue plastic. Attach fake fish, fake plants, etc. behind the plastic. Glue a box of fish food and a fish net to the top edge of the box. Wear all white clothes underneath.
Popcorn:
Take a large box, cut off the top flaps, make leg and arm holes, and attach straps so you can suspend it from your shoulders. Paint it with red and white stripes and write "POPCORN" on the front. Glue popped popcorn around the top of the box and all over your shoulders, neck and hair. Wear white make-up and white clothes underneath.
