Just giving a better explanation and adding some more from
Kaze-san's post:
Spoiler:
1. Chopper ate one of the Animal Fruits, the Human fruit. He can turn into half-human/half-deer and in other 7 different forms. Also, eating this fruit gave him the ability to talk and walk in two legs, like a human
2. Robin ate the Hana Hana Fruit. She can make parts from her body (like her arms) sprout from anybody (her included), like a flower. She has a kicking-ass fruit power that's almost unbeatable.
3. Mr.2 ate the Mane Mane Fruit (don't know what "mane" means). His power is to become physically identically like the person he wants (anyone). He gets back to normal if he touches himself with his left hand. Also, Mr.2 has a great memory, so after seeing someone once, he can turn into them anytime he wants.
4. Crocodile ate the Sand Fruit. He can control sand and turn into it.
Hope that answer your questions,
Raiden-ossan lol j/k