There are 4 secrets in the Halloween Catalog!
Here are some items (that I remember) they brought back:
Skeleton Suit: 450 coins
Clown Wig: 210 coins
Clown Suit: 450 coins
Clown Shoes: 300 coins
Magic Wand: 150 coins
Ghost Costume: 600 coins
New items:
Princess Hat: 300 coins
Princess Costume: 550 coins
Fairy Wings: 400 coins
Bee Antenna: 200 coins
Bee Wings: 350 coins
Bee Costume: 450 coins
Magician’s Cape: (Black cape with red on the inside.) 550 coins
To get the Fairy wings (400 coins), click on the Princess’ belt.
To get the Red Viking helmet, (750 coins) click on the head of the penguin diving into the bucket of paint. To get the Blue Viking helmet, (1200 coins) open and close the Red Viking Helmet window 4 times.
To get the Swim goggles, (220 coins) click on the Designer Glasses.
To get the Red guitar, (975 coins) click on the right blue roller skate’s wheels.
Pictures from Paintboy100 and Antras' Site.