Is mocking a friend (in a friendly way) forbidden?

I know it is not good to make faces of people and crack jokes about their personality etc. but if all of them are in a agreement that they won't mind it, can we make such jokes with them? For example, person A and B are two friends and they keep joking with each other. If person A copied some actions of B so as to make fun of him, and if person B does not have a problem with this, is it fine to do so?