I agree with Alexander Lewis" view that one of the main underlying themes in the movie is the confusion and division that Hedwig faces after the surgery of his penis. Like Hedwig, the Berlin wall is also divided, separating East and West Berlin. Coincidentally, Hedwig's mother is from the East, and his father is from the West. .
After Hedwig's mother throws his father out for molesting him, Hedwig gets a sex change to marry an American G.I. to leave E. Berlin. However, once his husband abandons him for another man, Hedwig is faced with another type of division. He is neither man nor woman. Instead of trying to identify himself, he decides to go drag, thus ignoring the aspect of identity. He never fits in any category, so he creates a new one. Obviously, however, he is not really happy with himself, and hasn't really discovered who he really is.
Hedwig hides his sadness behind his songs. In doing this, he avoids reality, but at the same time, still remains lonely. He find companionship in Tommy, a younger boy he is sexually attracted to. Hedwig creates an alter ego for Tommy, and his new last name is Gnosis, meaning "knowledge." This in itself is ironic, and it also a character division for Tommy. He knows Hedwig's songs, and he knows about his "one inch mound" (after he and Hedwig were becoming intimate), but he wasn't the person who created them, and he doesn't have the spirit that created the songs.
Tommy soon hides behind his alter-ego, even creating a cross on his head. Now having a mask to hide behind, he can go on, guilt-free, performing Hedwig's songs and passing them off as his. Hedwig uses Tommy as someone who he can use to continue to ignore his own sadness, shadowing him on his tour. This is ironic, because Hedwig is in search of truth, but at the same time, he is ignoring realizing the truth of who he is and his identity. Eventually, Tommy's guilt breaks through, and he apologizes to Hedwig for stealing his songs, adding Hedwig to writing credits on the back of the cd.