A live show on the bus (alt., on the train) put on by crazy or outspoken people (see, "Busnuts") who feel the need to act out their private junk on the bus, talk to the voices in their heads, or just generally make a scene for the enjoyment of others, on public transportation.
I saw a bus drama today when some busnut started yelling at a tourist for bumping into him.
A crazy or outspoken person on the bus (or train or other public transportation). A person who acts out their own private dramas on the bus, talks to the voices in their head, or otherwise puts on a show for other passengers (see also, Bus Drama)
Some busnut started yelling at a tourist on the subway for bumping into him.