Aginah is found in a desert cave in ALTTP 
http://www.zeldawiki.org/Aginah

and found his way back in AST. However, japanese programmers must have
forgotten to give him his original green outfit

- use aginah.ips to give him his green robe in the normal game (works for all weeks).
- use aginah_cutX.ips (x stands for the week number) if you use the intro/end patch. 
  This will change Aginah's robe in  the intro and end cut screens, too. 