In certain places in the world, you can encounter UFO's carrying things.
In order to do this quest you will need:
The prize for this is the PuPu Triple Triad Card.
There are 4 UFO's to encounter, each will be carrying something, they can be found in the following locations.
This quest is available until Disc 4 (Return via Portal)
Encounter #1:
Outside of Winhill is an area called Winhill Bluffs; here you can encounter the first UFO. Walk around until you find the UFO, it will be carrying a cow.
Encounter #2:
To the east of Timber is a sandy shore called Mandy Beach. Here you can find the second UFO carrying a Statue.
Encounter #3:
There is a big desert to the far east of the Centra Ruins called Kashkabald Desert. Here you will find the third UFO carrying a Pyramid.
Encounter #4:
To the east of Trabia Garden is Trabia Heath Peninsular. There is a small island off the coast where you will find the fourth UFO carrying a symbol.
Once you have seen all four UFOs, head to the Grandidi Forest; this is north of Esthar and east of Trabia Heath Peninsular.
You will see a Chocobo Forest here and some cliffs behind it.
Land on the cliff and walk around until you get into a battle with a UFO.
The UFO is weak and poses little threat to you but you have to defeat it; you will receive an Aegis Armlet for doing so.
After the scene, head to Balamb and walk about the Alcauld Plains until you encounter an alien, known as PuPu.
In this "battle" you can either defeat it to get an Accelerator or give it 5 Elixirs to receive the PuPu Triple Triad Card.