To encounter Ron "The Weasel" Copperhead, you must find his cabin. Defeating butlers, skeletons, button fellas or foxes in combat will advance the discovery of Ron's cabin. 6 must be defeated before Ron becomes available, but they need not actually be fought in the Zeppelin; e.g. you can receive progress via a Digitized or Greg'd red butler.
Progress messages (in this order):
After the fight, you explore the cargo compartment of the zeppelin. It's filled with a bunch of really boring stuff, but you do get a slightly better sense of the ship's layout.
You rifle through your fallen foe's possessions, looking for a clue as to the leader's whereabouts. You find a note reading Do not enter Ron's cabin for any reason whatsoever. From this, you glean that Ron is... in a cabin.
On the wall next to your fallen opponent, you see a map of the zeppelin, with an area marked Best Cabins. You note the location, assuming that Ron's cabin is probably one of the best ones, if not the best one.
After defeating your foe, you notice that one of the zeppelin's janitors has left his keyring on a hook on the wall. You grab it and unlock every door on the zeppelin before flushing the keys down the toilet. Take that, random janitor!
Having unlocked all of the doors in the zeppelin, you finally manage to figure out where the nicer cabins are. Unfortunately, you only have time to check a couple before you hear a guard coming and flee.
You finally make your way to the largest, most luxurious cabin in the zeppelin. You steel your nerves for the inevitable confrontation with Ron Copperhead.
If you do not defeat Ron Copperhead, he will go into hiding, and you will have to defeat 4 more of the above enemies to encounter him again. The progress message will always be the same in this case:
You check compartment after compartment looking for that weaselly Copperhead guy, but to no avail.
A ticket taker accosts you after the fight. Unable to produce a ticket, you are thrown overboard! You grab onto your familiar's invisible dirigible and float down safely.
Once you defeat Ron "The Weasel" Copperhead, the zeppelin will go up in flames. During every round of combat against a native Zeppelin monster, a chunk of flaming zeppelin will hit either you or the enemy, dealing hot damage.
If the chunk hits you:
A chunk of flaming zeppelin falls on you like a ton of hot lead.