Apart from the spoons, the thing that comes into my head whenever I think of the Grehans is the song Cricklewood.

Helen was definitely Bernie in the days I have in mind (1969-ish in the North-eastern folk clubs, where they were regarded as superstars) and the entertainment value was immense. Wasn't it her who'd take off round the room, playing the spoons on any available part of a member of the audience's anatomy? Great memories.

I located that YouTube video mentioned by Guest Maurice, and the Grehans' contribution is relatively short but since the clip runs to 37 minutes (dated but still fascinating, the remnants of an aborted Irish musical), it's still worth a look. Go direct to YouTube and look up O'Donoghue's Opera (there are other, shorter clips too by the look of it) or check it out at   
http://www.salutlive.com/2008/10/getting-round-t.html