Terraria updated to v1.1.2 today and added a new item for the Collectors Edition of the game. Players who buy the Collectors Edition will spawn with a 'Carrot' in their inventory. However, players who do not have the Collectors Edition will not. You can trade the item between versions but non-Collector Edition versions cannot use the item.
Here is how to set you current Terraria client as Collectors Edition:
Open Registry Editor (Start -> Run -> regedit)
Navigate to HKEY_CURRENT_USER\Software\Terraria
Add a new string key named "Bunny" without the quotes.
Set the value of this new key to "1" without the quotes.