Clinton,
I'm with you.

I particularly hate it when someone who wants to hear, say, "Early Morning Rain," instead asks me to "play a Gordon Lightfoot song;" then I comply by playing, say, "Cotton Jenny," and then they say, "Oh, no, that's not the one I wanted!"

Drunks in bars are not a lot different from seniors in nursing homes who have short attention spans and some short-term memory impairment.  Both groups will often:
•  request a song you've already played (maybe even just got through playing)
•  keep requesting the same song every 5 minutes
•  interrupt you in the middle of a song to request a different song [right, AllieKatt?]
•  request a song and then get distracted in conversation [or even get up and leave, sometimes] as soon as you start into the song.

I, too, am annoyed [or at least puzzled] when I'm doing a theme and someone asks for something completely out of step with it. E.g.,  during a Christmas program someone requests "Danny Boy" or during a St. Patrick's program someone requests "some country/western"].  Or when the program [or the venue itself] calls for something other than contemporary hits and some of the [usually] younger set keep asking for whatever has been in the charts in the last two or three years.   I don't mind so much being asked, but some folks are so narrow that if you don't know [or won't insert into the program] whatever song they come up with, they won't even listen to what you do play/sing.

Strictly as an aside, folks, the fact that Shel Silverstein was Jewish is not as relevant re "The Unicorn" as the fact that he was a Jewish American and, as far as I know, not an Irish-Jewish American.  There are Irish Jews [James Joyce wrote about one in "Ulysses, e.g.], Irish-Canadian Jews [ask Paddy Graber], and Irish-American Jews [I'm told that George M. Cohan was one].  If an Irish Jew writes music is it any less "Irish" than music written by a Christian Jew?  [For purposes of this thread, let's just call this a rhetorical question.]
 

Rick F.,
I often have folks ask me to play a song I only partially know--e.g., maybe the first two lines, the chorus, and maybe the last two lines.  I tell them that's all I know of it.  Then the requester tries to enable me to sing it by singing the first two lines, a bit of the chorus, and the last two lines!

Genie