I'm a a Patronus and I will tell others which spirit animal they have in their patronus, in the wizard world. The patronus is also the form that a person take when they turn animagus If they learn transfiguration. If a Wizard or witch falls in love a patronus can change to match their loved ones, because their happiest memory changes, or if they experience a situation that makes them feel a strong positive emotion like having children. Though for this to happen, the memory has to be very strong.