It took me a while, but I got there. My late Grandfather (b.1895) told me a little riddle from his childhood which was:
ABCD Goldfish
MNO Goldfish
SDR Goldfish

You will almost certainly work it out but, in case it's too British, it's:
'Abe, see the G.'
'Them ain't no G.'
'Yes they are G.'