When you drop one item in creative then you pick it up, you pick up two instead of one.
What I expected to happen was...:
Pick up the one item I dropped.
Steps to Reproduce:*
1. Open Inventory in creative
2. Hover mouse cursor on the item you want to dupe (it needs to be stackable)
3. press "Q"
4. Close inventory
5. Pick up the item
6. The number of item added by two instead of one