Mr. Store is a high-class store in Market Square. Mr. Shopkeeper doesn't deal in such piffling currency as Meat; instead shoppers trade in Mr. Accessories to buy things. In addition to the regular offerings, there is a Special of the Month which changes monthly.
Hi there. I'm Mr. Shopkeeper, and this is Mr. Store. Here, you can trade Mr. Accessories for other groovy stuff.
While in Hardcore, players can place Mr. Store familiars into their Familiar-Gro™ Terrarium and put books into their Mystical Bookshelf. However, trying to equip a Mr. Store item while in Hardcore results in the following message:
You can't equip your <item name> while in Hardcore mode.
On each anniversary of Mr. Store, both the Blood-Faced Volleyball/Leprechaun-type hatchling and the Leprechaun/Fairy-type hatchling are replaced with new, but functionally identical familiars.
On January 31st, 2007, Jick released the February Item-of-the-Month early. This resulted in both January's and February's items being available for one day.
On April 1, 2009 the tiny costume wardrobe appeared in the Mr. Store with the message "NOTE: This item will appear in Mr. Store every April 1 from now on."
References
In the Mel Brooks Film Spaceballs, the bridge of Dark Helmet's SpaceBall One had all of the important systems (Radar, Coffee, Rental) labeled as "Mr." (System), which is itself a reference to the brand Mr. Coffee.