Welcome to planDisney, Katherine!
It sounds like you have a trip to the Disneyland Resort planned during
Halloween Time! This is one of my favorite times to visit the parks! I love all the autumn decor and the frivolity that this season tends to bring with fun costumes, special treats, and seasonal overlays on attractions. The Oogie Boogie Bash – A Disney Halloween Party takes place on select nights in September and October at Disney California Adventure Park. If you are visiting Disney California Adventure Park and don't have tickets to the party taking place that evening, you will be asked to leave the park by 6:00 p.m.
If you already have Park Hopper tickets, then you can most certainly hop on over to Disneyland Park when Disney California Adventure Park closes for the party (subject to park capacity limits). If you have a one park per day ticket, you can upgrade it to a Park Hopper ticket at a ticket booth for an extra fee. Or you can enjoy the evening in the
Downtown Disney District eating dinner and doing some shopping--no extra ticket required.
Another option would be to switch your
theme park reservations so you are visiting Disney California Adventure Park on a day that doesn't have a party in the evening. However, I highly recommend checking to see if there is reservation availability by viewing the
theme park reservation availability calendar first. If there is availability and you want to change your reservations, you will have to cancel the theme park reservations you currently have in place and make new ones.
I hope this information was helpful! Have a ghoulishly good time at the Happiest Place on Earth!
-Linda