Their diet is mainly of `` Tubby Tustard '' ( which is sucked through a circular straw ) and `` Tubby Toast '' . Their diet seems to be almost exclusively `` Tubby Custard '' mispronounced as Tubby Tustard by the characters ( which is created by a Tubby Custard machine , looking like some sort of DJ-gramophone , complete with light effects . The custard is consumed by either dumping the bowl into one 's mouth , or sucking through a spiral straw ) and `` Tubby Toast '' ( circular toast with a smiley face on it ) , and they are spectacularly messy eaters .