As I understand Cracker Jack (crackerjack) is a mixture of peanuts and popcorn.
Could you please tell me whether it is countable or not (uncountable)?
If it is countable, I can say "a Cracker Jack" and "Cracker Jacks". If it is uncountable, I can only say "Cracker Jack".
I'll go with Paul. Uncountable Cracker Jack sounds better to my American ear.