The Sad Skeleton struggles to make friends, leaving him sad and lonely. Talking about his feelings with Dave the Bat, he understands his emotions and slowly begins to relate to others around him, his sadness turning into acceptance and happiness.
The Angry Alien is angry and alone. He's convinced being 'different' means no one can like him so he shuts himself away. A chance meeting with Jel the Turtle shows him how to deal with his 'big' feelings and let others in.