Here is a list of all Tamagotchi-iD passwords we know of so far.
(I'll update this list as new ones are revealed.)
To enter a password, activate the connection (heart) icon in the upper right corner. A two-page menu will appear. Password is the top entry on the second page. When you select Password, a sub-menu displaying two options will be shown. For passwords consisting of numbers (0-9), select the top option. For passwords consisting of leters (A-Z, and spaces), select the bottom option. If the password is less than 10 letters long, fill in the empty places at the end with spaces.
60576 01893___McDonalds Living Room available for 1000 GP at Gotchi Interior Shop
71249 35698___Jewel Living Room available for 3000 GP at Gotchi Interior Shop
87094 91352_W_Stage & Mic available for 2500 GP at TamaDepa
28585 37149_W_Cell Phone available for 1500 GP at TamaDepa
12619 42038_W_Tiara available for 5000 GP at Accessories Shop
54925 74983_._Eco Bag is added to Special in the Treasure Chest
86802 48153_T_Cotton Candy available for 110 GP at TamaCafe
32634 70719_A_Fruit Parfait available for 350 GP at TamaCafe
68592 76210_M_Aquarium Living Room available for 1500 GP at Gotchi Interior Shop
91256 86673_A_Flower Headdress available for 2700 GP at Accessories Shop
70315 29240_T_Matryoshka available for 800 GP at TamaDepa
92467 50941_A_Resort Living Room available for 2000 GP at Gotchi Interior Shop
50749 56528_L_Gyu-udon available for 200 GP at Convenience Store (note: this password doesn't work on the Lovely-Melody ver.)
TAKEOUT_____._Potato (French Fries)
RAINBOW_____O_Nuggets (Chicken McNuggets)
LOVELIN_______Sweet Corn (Nibblets)
The eight McDonalds menu items above are not food that can be consumed. After any of these passwords have been entered, an entry for "McDonalds Bag" appears in the treasure chest menu. Activating it shows a catalog of the item(s) you've entered. When one is selected, Makudotchi appears, pulls the item out of a McDonalds paper bag, then asks a question about it. After a moment, Makudotchi provides the answer, pops the item back into the bag, then leaves.
Note: Any of the above with a price in the description means the password only adds the item to a shop's inventory. If you want to use the item, you'll have to send your Tamagotchi character to that shop and purchase it. For example:
"60576 01893 McDonalds Living Room available for 1000 GP at Gotchi Interior Shop"
This means that after you enter the password 60576 01893, the McDonalds Living Room will be added to the Gotchi Interior Shop's inventory. If you want to decorate your room with it, you have to purchase it from the Gotchi Interior Shop, for 1000 GP.
Thank you Tama-Star_Girl for finding the password for the Tiara.
Thank you tarokaja for finding the passwords for Cotton Candy, Fruit Parfait, Aquarium Living Room, Flower Headdress, Matryoshka, Resort Living Room, and Gyudon.
Edited by binary, 02 December 2010 - 07:48 AM.
added note about Gyu-udon password