As a carrot
After Bulma, Goku and Oolong left Frying Pan Mountain, they stopped in a small town for fuel.
Bulma went shopping for some new clothes, since she was still wearing that bunny outfit Oolong gave her.
After she bought a new outfit, two men from the so called "rabbit gang" started flirting with her.
Bulma, clearly not interested, asked Goku to get rid of those guys. The gang called their boss; Boss Rabbit. Boss Rabbit asked Bulma to give her the five, and Bulma thought something like "whatever" and slapped his hand. Suddenly Bulma changed into a carrot! Goku fought with Boss Rabbit and won eventually with Yamcha's help. Boss Rabbit changed Bulma back and Goku gave them a small trip to the moon, where they made candy for little children (some japanese legend).
Oozaru snack
The group was locked in Pilaf's castle. Goku looked at the full moon and transformed into an oozaru. He even tried to eat Bulma! Fortunately this didn't happen. This also only occurred in the anime (that Bulma was almost eaten).
As a chocolate bar
In Dragonball Z, Majin Buu came when he located God's palace, where everyone was.
While Gotenks and Piccolo were locked up in the room of Spirit and Time,
Buu changed everybody at the palace into chocolate. Bulma DID get eaten this time, and this was also the first time that she died.