I guess, maybe, they're still running with the cat theme because 9th anniversary and nine lives? I dunno.
There are Trick or Treaters roaming Millennium City. When you talk to them, they will either say "ToT" and maybe give you gift bags or turn into monsters and attack. The monsters are: Frankenstein, Ghost, Black Cat, Mummy. This is part of the daily mission, so talking to the event guy and killing 10 per day gets you some extra goodies.
There are other things going on. Something in Canada, I think, with wolves/werewolves and the Kiga thing. Also, each week they're going to be adding more. Next week is the zombies and rescuing the heroes missions. There's some PVP thing, as well, but I don't PVP.
So far, the cat AF is the only thing that interests me with the event. Other than the general spookiness of the event, it has never really impressed me. I remember last year I got bored with the hero rescue missions and stop bothering after a few days. The event store has the typical things to buy: vehicles, costume pieces/auras/transformations, etc. None interest me very much. I got the black semi-transparent flying cycle last year, so nothing left to buy.