Also, there was a Creatures radio show at one point! There aren't any recording from the show, but the original site has been archived. I found it while searching for radio agents, and thought it was too neat .
There aren't a lot of radio agents, but the C3/DS ones are pretty good. Two of them are just the beat box from C3 in an object pack. The one from the connective agent pack does allow you to inject it in DS standalone, if you have C3 installed. The survivor and portal radios are probably the most interesting radios in this bunch. They play different songs, and the survivor radio even makes the Creatures around it say something.
Tape Player by Mokus
Hanson Radio by AntiNorn
Xmas radio by Celeste
Portal Radio by Ghosthande
Survivor Radio by Ghosthande
Beat Box (in the More Pack) by Ylukyun
DS Beat Box (in the DS Connective Agent Pack) by Mirality Systems