What do you call a cod that's been battered and breaded and fried? Fish fingers; I'm a stickler for the Queen's English.

Explanation: there is a lot to unpack here. A cod is a kind of fish, which is often cooked in the form of a kind of fried cake. Different people call this different things: in the UK and the Commonwealth we tend to call them "fish fingers", but as I understand, in the United States they are called "fish sticks". Other countries might even use non-English names altogether. By calling them "fish fingers" we are performing a deliberate undermining of the structure of the pun because they aren't "sticks" at all! We then make a reeling recovery by drawing attention to the language barrier and use the word "stickler", which happens to start with the same letters as the word "stick", but means an entirely different thing, which is "a person who is very particular and cares a lot about something that is not necessarily worth caring about quite so much". By using the word "stickler" instead of "stick", we have broken the very rules that a "stickler" would care so much about!