Well, you've heard about the Boston Pee Party, and the Boston Pee Party #2. But this one could only happen in a Monty Python movie -- or in London, England. Turns out that the bomb squad was called out in East London because a streets worker discovered the item to the left in a street drain (undoubtedly washed into it during a downpour), saw the word 'grenade', and... well. You know the rest.
It is unclear whether there are any killer rabbits involved in this story, but given the details, it seems unlikely.
-- Badtux the Snarky Penguin