What lines prove that Bottom has become used to being loved as a donkey in Shakespeare's A Midsummer Night's Dream ?
While there really are not very many scenes with Bottom as a donkey being loved by Titania's, it is certainly within Bottom's character to enjoy any attention he receives. He particularly enjoys being the center of attention. Hence, there are certain lines that tell us just how much he is enjoying the attention he is receiving by being a donkey that Titania is in love with.
We especially see just how much Bottom has become used to being a donkey and even enjoying it when we see him giving orders to the fairies. Titania has assigned three different fairies to attend him, and he very quickly becomes used to being waited on hand and foot. He commands Peaseblossom to scratch his head, Cobweb to hunt down a bumble bee for honey, and for Mustardseed to help Peaseblossom scratch his head (IV.i.7-26).
Another clue telling us that he has not only become used to being a donkey but has actually fully become a donkey is that he begins acting like one. We especially see him acting like a donkey when he asks for hay and oats to eat, as we see in his lines:
Truly, a peck of provender; I could munch your good dry oats. Methinks I have great desire to a bottle of hay. Good hay, sweet hay, hath no fellow. (31-33)
Hence, from these two clues we can see that he has fully become a donkey and is immensely enjoying the attention of being loved as a donkey.