In the spiritual world service is voluntary, some devotees want to serve Krishna as flower; so they become flower there. If I want that, to be a flower I shall lie down at the lotus feet of Krishna, then he becomes flower, voluntarily, and he can change his, from flower to human body. That is spiritual life. There is no restriction. If some devotee wants to serve Krishna as cow, he serves Krishna as cow, as calf, as flower, as plant, as water, as ground, field, or as father, as mother, as friend, as beloved, anything. It is
inconceivable, yet a fact.

From Srila Prabhupada’s lecture on SB 6.1.1-4, Melbourne, Australia, May 20, 1975