Denny is the neighbor of Johnny and Lisa. He frequently shows up to their apartment unannounced and attempts to ingratiate himself into nearly every aspect of their lives, including their lovemaking. Denny is just the worst.
He also manages to run afoul of the local drug dealer, Chris-R, apparently buying some unknown quantity of generic "drugs" and neglecting to pay for said drugs. God Denny, can you do anything right?