Bonnie's Toy Box is where Bonnie Anderson keeps her toys.
It looks like a brown basket-shaped box.
Toy Story 3
In Toy Story 3, Bonnie was playing in the box with Woody, Mr. Pricklepants, Dolly, Trixie, Buttercup, Chuckles and Totoro.
Toy Story Toons
It also appears in the Toy Story Toons shorts Hawaiian Vacation and Small Fry.