From the Super Mario Wiki
The Shamrock Inn is a small stone cottage located in the Shamrock Kingdom, that appears to serve as a bed and breakfast inn. It was seen in The Super Mario Bros. Super Show! episode "Mighty McMario and the Pot of Gold".
Not much of the Shamrock Inn is seen, save for the kitchen on the main floor. In the kitchen there is a table with benches for people to sit at, as well as a fireplace, and a chandelier. Accommodations at the Shamrock Inn are apparently very cheap; a sign pointing upstairs reads that rooms only cost twenty-five cents.