Went to Everland for a friend's birthday.
For Halloween (which is aparently a month-long event) they run parades and have different things set up all through the park.
Everland is about a good 1 hour 30 min bus ride from central Seoul. There are some good rides there but the best part of the theme park is the "Safari Ride" and the area of the Victorian Garden.
This famous theme park combine many things in one. There are zoo, water park, theme park for rides. All in one place. I think this is Disneyland of Korean.