The Miracle Growth Baby is a baby brought to Deep 13 to demonstrate the Mads' Invention Exchange preceding Experiment #306, "Miracle Baby Growth Formula". It works better than expected, growing the baby to full adult size instantaneously. After the experiment, the Mads argue about changing the baby's diaper, leading the baby to push the button himself.
During the Invention Exchange before the next experiment, it is the Miracle Growth Baby who demonstrates the Mad's latest creation, the Alien Teething Nook. At the end of the experiment, the baby breaks the button, causing the end credits to start and stop several times.