In the north of Hearthome City, there is a special area that you can only enter with certain Pokémon. There are 11 Pokémon out of the 493 Pokémon that are able to enter Amity Square. These Pokémon then get out of their Pokéballs and follow you around. They are the Pokémon below;

 

There are many people and things spread about Amity Square including several items such as TM45 and the Spooky Plate. It's worth having a look around.
However, the biggest thing of note is that the Pokémon you have following you will end up picking up items every 200 steps. All you have to do is talk to it and take the item off it. These items are all Contest Related, mostly being Contest Accessories, but you can sometimes pick up berries. Below are what can be picked up and their rarity for each Pokémon

What Can Be Found

Hover over for Accessory Name

#025 Pikachu #285 Shroomish
Common Rare V. Rare
Orange Fluff Brown Fluff Small Leaf Red Feather Yellow Feather Yellow Fluff Glitter Pebble Big Scale Black Moustache Purple Scale

#035 Clefairy #300 Skitty
Common Rare V. Rare
White Fluff Orange Fluff White Feather Round Pebble Small Leaf Blue Scale White Beard Thin Mushroom Big Scale Stump

#052 Psyduck #417 Pachirisu
Common Rare V. Rare
Jagged Boulder Snaggy Pebble Brown Fluff Rounder Pebble Black Moustache Shed Horn Narrow Scale Mini Pebble Green Scale Thick Mushroom

#255 Torchic #425 Drifloon
Common Rare V. Rare
Pink Fluff Red Feather Yellow Feather Black Beard Narrow Scale White Fluff White Moustache Shed Claw Narrow Leaf Purple Scale

#427 Buneary #440 Happiny
Common Rare V. Rare
Pink Scale Shed Horn Pink Fluff Yellow Feather Shed Claw Black Fluff Jagged Boulder Big Leaf Green Scale Black Pebble

Berries
Rare V. Rare
Cornn Berry Magost Berry Rabuta Berry Nomel Berry Spelon Berry Pamtre Berry Watmel Berry Durin Berry Belue Berry

Note: Information on Jigglypuff will be added as we get it