A few buildings in the game are called "Helper" buildings. These buildings will give you one needed item along with their usual profits.

How do these buildings work:

1) items drop RANDOMLY from these buildings;

2) you can't receive from these buildings:
- Items needed for the crafts in production buildings, for example - Pillow for the production of the Sofas at the Furniture Factory;

- Items that you need to ask friends for;

- items that are produced in quests (for example, as in Lemonade factory quest);

3) you can receive from buildings:

- Items required in active quests, including quests with random tasks;

- Items for decors in the Academy of Magic;

- +3 energy, if you do not need items in active quests or for the Academy;
The current list of Helper buildings in Supercity:
Romantic date
Tree house
Dracula's Castle
Neuschwanstein Castle
Art Gallery
The Emir’s Palace
Indian Palace
Santa's sleigh
Rabbit meadow
Omnibus depot
Train Robbery
Yacht transportation
Statue of Maat
Agronomist laboratory
Mad Tea Party
Chariot Workshop
Elf Houses
Mysterious Castle
Indian market
Dinner Date
Holiday “Find all Eggs”
Kite Workshop
Residence of Harmony
Reserve security
Warning Bell (Obtained only by activating notifications on the portal. You can collect profits ONLY from the portal)
Mayan Temple archeological dig
Town meeting hall
Seafarer’s Haven
Drakkar Restoration
Bonsai studio
Cloud-high Resort
Haunted hippodrome
Tolek construction
Christmas clock tower
"Penguinarium" Research Center
Tsar’s Residence
Maiden’s Tower
Sculptor's studio
Japanese gardens
Easter Aerodrome
Florists's house
Solomon's Temple Excavation
Citadel of Seekers
'Guitar Riff' Radio Station
Changdeokgung Palace
“Board´em!” ride
Sultan's Palace
Broomstick Race    
Harvest in the Tropics  
Christmas Depot
City Herbalist's Houses
Factory of Extraordinary Fragrances
Druid Village
Easter Party
Luxurious Palace
Georgian Fortress
Northern Spa Center
Dollmaker's Workshop
Han’s Palace
Caramel Garden
Labyrinth in the field
Catnip Farm
Clock Foundry
Sami Village