Quote from Ross in The One with the Girl Who Hits Joey
Ross: [angry] I thought you were my best friend. This is my sister. My best friend and my sister. I cannot believe this. Chandler: Look, we're not just messing around. I love her. Okay, I'm in love with her. Monica: I'm so sorry that you had to find out this way. I'm sorry, but it's true. I love him too. Ross: [overjoyed] My best friend and my sister! I cannot believe this!