an old favourite formation callsign was "Potato"... checking in as "Potato 1, Potato 2, Potato 3, Potato 4...
A10s when based in the the UK used pig related callsigns... when Sausage Formation where inbound for a practice approach and overshoot (go around)... the controller asked them if they would be prepared to roll from the approach... for controller training
Truth was it was simply becasue he wanted to make the liaison call to Tower... "10miles Sausage Roll" (doesn't work with phraseology "touch and go" though?)
I'm sure there are hundreds more...?