Don’t have a cow, man!
An admonition spoken to a male seahorse who is concerned that he's gonna give birth to sea CATTLE instead of sea HORSES.
Most creatures reproduce though the female, with the male providing fertilization of her eggs while their still "in her oven". But male seahorses do somewhat the opposite --- the female deposits her sterile eggs into the male's sperm-filled egg-pouch, where the eggs are fertilized and remain till they hatch. Once in a while, though, something goes wrong with the process, and the male becomes concerned that his eggs are turning into aquatic cattle instead of horses, prompting others in his clan to anxiously admonish, "Don’t have a cow, man!"