Once you reach the beach, which is approximately 30 minutes into the game, you will play a game called "Truth or Slap". When Clarissa asks Ren if they are ready, respond "Ooh, Good One." Next, respond "He's Lying!" Then, respond "He Told Me He Liked Her!" Finally, respond "Yay!" for Ren to get slapped and to get the "Renjamin Spanklin" achievement.