First...I assume that you know that the line I was referring to was one of Groucho's.Second,the only law firm I recall from the Stooges was "Goldman,Goldstein,Goldberg and O'Brien".And the guy answering the phone,who had a Yiddish/Hebrew accent,said at the end of his greeting...in that Yiddish accent..."O'Brien speaking".Funny stuff!
I guess you must have missed that episode.
http://en.wikipedia.org/wiki/Dewey,_Cheatem_%26_Howe
http://www.123posters.com/stooges7.htm
https://www.youtube.com/watch?v=pVdUU6S87dk