Doctor Who special effects

Stacey stands in her bathroom in front of the sink. She has taken a diet pill. She doesn’t feel so great Photograph: BBC

The birth of the Adipose. This sequence was hand animated Photograph: BBC

A rig was used to bulge an actor’s trousers before an Adipose is born and slips out. Special effects added the Adipose later Photograph: BBC

A storyboard used by the production crew in creating the shot of an Adipose struggling out of the back of Stacey's jeans Photograph: BBC

A storyboard used in planning the shot where an Adipose is born Photograph: BBC

The Adipose are on the march through a building in this computer test, which uses the Massive programme in a 'density test' to determine if a large enough crowd of the critters has been created Photograph: BBC

When the script called for the Adipose to be hit by a car, a 'dynamics test' was employed to see if they would go splat or bounce along Photograph: BBC

When a group of cheering Adipose were needed, a 'movement test' determined if the spectacle would look realistic Photograph: BBC

Originally the Adipose were going to move rigidly like a Roman legion, but the Massive programme allowed a crowd of running Adipose to move independently of each other. The 'flocking test' checks how the running crowd interact with each other Photograph: BBC

If the Adiposes were forced to walk on hilly ground, would they still stay upright or sink into the ground? The 'terrain test' simulates how one would behave Photograph: BBC