As Fointaine (one of my personal favorites), I loved it when he/she sang "Around the World in Eighteen (expletive) Days". The story "Fontaine" tells about leaving the US to travel to Europe was funny, but then it turns depressing when he/she talks about and describes visiting the Anne Frank Museum; She learns about Anne Frank; How she and her family hid from the Nazis; Being found by the Nazis and finds out about her eventual fate. It's amazing how she goes from funny to sad quickly.
Another favorite character was the "Surfer Chick". If you never saw her doing this and just listened, you may have never guessed it was Whoopi. The voice was very believable. It was funny when she would say "He said okay; I said okay; Okay, Okay, Okay"; Very funny. But just like "Fontaine", the story would go to funny to depressing when she talks about being pregnant; Her boyfriend leaves her when he finds out and she has to make a tough decision of either keeping and raising the baby by herself at a young age or getting an abortion.
The two characters mentioned stood out the best more than any other, because although they may be fictional, they were very believable. You laughed during the funny parts and you could feel the pain and hurt during the sad moments.
This early performance by Whoopi was one of her best. I believe this performance i out of print, but if you manage to find a copy; Watch it. It's worth it.