Are we entirely sure that "fish fingers and custard" isn't the name of a '70s detective duo? Detective Fish Fingers lives on the edge, always breaking the rules. Detective Custard is the no-nonsense, plays-by-the-book cop. Together, they're unstoppable. I'd tune in for that. If there's anything television needs it's more cop shows.
In reality, fish fingers and custard is the salty, fishy, yet sweet treat that is apparently very delicious. This is something I've eaten when I accidently thought that the custard was dijon mustard. What a rude awakening, but surprisingly delicious. It's just not so delicious when you think you're about to taste something else. It's like when you think you're about to drink a bottle of water, but then you find out it's a bottle of vodka you hid because of your secret alcoholism.