Tubby Custard is a pink, soup-like substance that Teletubbies eat, however it is reviled by every other organism. It tends to show up in almost every video where a Teletubby appears.
In Cooking with Bowser and Mario 2! it is revealed that the main ingredient is marijuana. Adding a Super Mushroom to the mix will cause a chemical reaction that creates Shrek. This contrasts with SM64 Bloopers: Where the Wild Teletubbies are, which shows that the custard is created by inserting Doritos into a processor. It is the main ingredient Tubbie Wonka uses for spaghetti.