When a bit annoyed or disappointed, my mother used to say, "Ho hum, pig's bum!" Unfortunately, I accidentally blurted this out one morning while among my 8yr old pupils. They roared with laughter and kept saying it themselves. I then invented a less rude version, "Oh dear, pig's ear!" in the hope they'd use that. But the 'pig's bum' one lived on in my classroom! (Mother was Irish, so it may have been an Irish expression)