I'm not sure about the Pirates but certainly the Mikado's little list has been tweaked every time I've seen it. Also, it's been changed from ancient Japan to very contemporary.
Saw it once with Eric Idle, with Bill Oddie and with Jasper Carrot, I think.
Eric was born for the part; very jolly hickey sticks, anyone for tennis in a dashing sort of way. I think Bill had to use a megaphone. Mrs Tag says the Carrot was superb.
Thinking about tomorrow I'm sure the modern major generals song gets tweaked.
PS. Don't get the wrong idea; I much prefer the likes of Verdi, Mozart etc.