Lol. Yeah, sometimes we used to chuck the hockey-puckified fish patties at each other when there were no customers that could see.
Also, I remember back in the day on Good Fridays we sold a disproportionate number of FOF and a disproportionate number of Double Quarter Pounders.
And yes, the two burgers were tested on a small scale.
https://www.tastingtable.com/2053261/mcdonalds-filet-o-fish-competition-pineapple-sandwich/