Cardboard Box is the thirty sixth episode of the first series. It first aired on October 25, 1999.
The Tweenies are bored with their toys so Max suggests that they play with the cardboard boxes he has left in the garden. At first they are unimpressed, but soon the Tweenies realise that a box can be anything they want it to be. Soon they have created a cardboard box train which takes them to space, under the sea and into the jungle.