To the Lab!!
Right near where the Broken Harmonica is found ( check the map ) there are a number of Starman Super enemies. These will drop Poo's first and only weapon, the Sword of Kings!
Just walk back and forth the area where you found the Harmonica and you'll have several Starman Super appear repeatedly. Just be careful for the Atomic Power Robot since they explode and can really drain your resources.
Starman Deluxe ( Battle )
After the battle is over, you go back to find that your friends have been released.
Talk to everyone to receive their thanks.
Apple Kid will tell you that the Overcoming Shyness book that he borrowed has actually been returned to the Onett Library.
The Mr. Saturn has a Saturn Ribbon that you can equip for Paula.
If you have an Exit Mouse, now is the time to use it.