Ryan, Marissa, Seth & Summer.
The Core Four (also known The Fab Four), was the name of the group, consisting in : Ryan Atwood-Cohen, Seth Cohen, Marissa Cooper, and Summer Roberts. The group was practically inseparable and always supported each other ever since becoming friends.
Ryan, Marissa, Seth and Summer walking on the beach.
The Core Four in : The Mallpisode.
The Core Four on their graduation day.
The Core Four together one last time in the episode : The Graduates.