Somehow the igloo basement duplicates its items in the brewing stand and flower pot. It is weird and kind of an awesome bug if you want to keep a weakness potion for the 'zombie doctor' achievement.

How to reproduce:
1. type in the command /locate igloo
2. teleport to the igloo
3. go down the basement
the item duplicates where the flower pot and the brewing stand is
Note: the located igloo does not always guarantee an igloo basement. A seed that always guarantee a igloo basement is:
42

Credit to WRSomsky for the seed