In reverse order of appearance:

Cat:  Red Battler  (Which was odd since the cat was blue)
Rei's Grandfather:  ? Hino  (He is never referred to by his first name so...)
Motoki's Girlfriend the Entomologist:  Reika 
Artist:  Yumeno Yumemi (In Japanese she didn't have two names, she just
	lived reclusively and kept her real appearance a secret)
Precog Boy:  Urawa Ryo
Minister:  They never actually got his name.  However he was a gaijin, so you
wouldn't have to work too hard to come up with a name for him.
Telekinetic UFO Catcher Guy:  Believe it not: "Joe".  

http://www.win.or.jp/~doi/smoon