My dark side, my shadow, my lower companion is now in the back room blowing up balloons for kids’ parties.

Meaning of the quote

The quote is talking about how the negative or "dark" parts of Gary Busey's personality are now being used for something more positive and lighthearted, like blowing up balloons for children's parties. Instead of letting his "shadow" or more troubling side control him, he's found a way to use it in a fun and harmless way.