Nothing really,you just get the satisfaction of getting all 28 Unown.
nothng happens
Nothing happens if the unown you catch can be arranged to spell water.
In the games that came before heartgold and soulsilver, I don't believe anything special happens. In Heartgold and Soulsilver, you can now catch the last 2 unown (the "!" and the "?") in the Hall Of The Ruins Of Alph. Then the scientist that gave you the unown recorder comes out and gives you a pat on the back...
You have to catch all 26 unown and talk to the scientist a few times for additional pages.
in the cave!
Nothing, sadly.
hidden power
the unown say "our friends look up and heartily congratulate us"
You pat yourself on the back because you have no life whatsoever..
nothing happens you just have them
After collecting all 26 Unown, talk to the scientist and he will let you print out your Unown shapes.
The tunnel on top the ruins is accessible.The tunnel is where you catch the ? and ! Unown.