Kevin,

Mark Twain is Jimmy Buffett's favorite author and he has always
acknowledged Twain as the inspiration for many of his songs.  Some
years back there was a very good "Jimmy Buffett Literary References"
page on the web that documented all of the Twain references.  That
page doesn't seem to be available any more, but here's an example
from an interview:

Pageonelit.com: I love the album Barometer Soup. Where'd you get
the name?

Jimmy Buffett: Mark Twain. If you're gonna borrow, borrow from the
best.

http://www.pageonelit.com/interviews/JBuffett.html

Barometer Soup is the album with the song with the wrinkles quote:

Barefoot Children In the Rain
http://www.twin-music.com/lyrics_file/buffett/bar/bare.html

It also contains at least two other Twain-inspired songs:

That's What Living Is To Me
http://www.twin-music.com/lyrics_file/buffett/hot/that.html

Remittance Man
http://www.twin-music.com/lyrics_file/buffett/bar/rem.html

Instead of condemning Buffett for stealing from Twain, it might be
better to ackowledge Buffett as a popular artist who has been
influenced by Twain.  Heck, you might even want to add his album to
your collection. :-)

Jim Zwick