Can I include previously prepared content for Game Jam into my Game Jam project?

Can I include previously prepared content for Game Jam into my Game Jam project?
For example, can I prepare a main menu widget before game jam starts and then include it in my gamejam project?

You’re going to get a lot of fuzzy answers here, I think. Mostly because the game jam rules are bent by a lot of people.

Technically, what goes into the jam, should only have been produced within the jam period.

Having said that, I’ve seen entries ( and winners ), who have obviously submitted almost finished projects they must have been working on for several months!