Hi there Amy,
Welcome to planDisney and thank you for your question! Even if you're just passing through, I'm happy to hear you'll have time to stop by the Happiest Place on Earth on Halloween. It'll be such a fun way to celebrate!
Oogie Boogie Bash - A Disney Halloween Party is a separate ticketed event and unfortunately, these tickets are sold out. Therefore, when Disney California Adventure Park closes for the day at 6:00 PM, you will need to exit that park.
However, what I would recommend is purchasing the
Park Hopper option with your ticket! That way you can spend the morning and afternoon in Disney California Adventure Park and then hop over to Disneyland Park in the afternoon until this park closes later that night. That's typically what I do when I visit on days when there is a special event in one park!
Additionally, make sure to keep an eye on the
Disney Parks Blog and the
Disneyland Resort mobile app as you get closer to your visit. These are the best places to check to see if there are any fun extra things that will be happening around the Happiest Place on Earth on Halloween day.
Thanks again for your question, Amy! I hope you have a wonderful visit to the Happiest Place on Earth.
Have a Magical Day,
Greg