I started examining this event here, so here is what I have learnt since ...
OK so Catrina and Champman are both in faction city graveyards. Nice and easy.
At 01:00 I'll have a rather large bet that there were shit loads of people in the graveyard and that there was a fucking wooly mammoth sat on top of the NPCs.
No problems. /tar catrina (cos there is always some twat who created a level 1 called catrinna) and then /dance. BANG you have the achievement.
Then /tar Chapman and then hit the button you have bound in your keybindings (Under Targetting Functions) to interact with target. Buy the flowers off him and then bread recipe and then make the bread.
Equip the Orange Marigolds and then use them. A Cheerful Spirit will appear and will want some bread of the dead. That you have just made from the simple flour and ice cold milk you brought with you.
Accept quest and then hand it in. You now have the Macabre Marionette pet that only lasts for the 2 days of the event.
Now spam /1 /s and /y that you are selling bread for 5g a piece and rake in the gold :)