ORIGIN:
Just in case you guys don't remember, at the very beginning of the game when you see Hayner, Pence, and Olette while you are teamed up with Axel, Axel explains "friendship". Roxas asks why Pence and Olette didn't mind Hayner pushing them around and Axel explained that it was because they were friends.
Later on in the scene, Axel calls Roxas his friend and asks if him if he would like to go out for ice cream. Roxas misunderstood and thought that being friends meant having ice cream together.
So there you have it, the whole entirety of "Who else will I have ice cream with?" translates to "Who else will I be friends with?"
This scene is found at the end of a Twlight Town mission called "Eliminate the Guardian"