Big Ben is a squirrel found sleeping on the nut sorting machine during the Easter 2009 and Easter 2010 events. He will work on the nut sorting machine if you give him and his workers 25% of the sorted nuts. You will need to teach him and the other squirrels how to work the nut sorting machine.
The name, "Big Ben", comes from a (bell/clocktower) landmark in London. The name could also refer to a builder, Big Ben, who hung the bell in the Big Ben.
During the 2009 Easter Event quest Big Ben and his workers do not like to be called vermin.
During the 2010 Easter Event, a part of the dialogue between you and Big Ben, the player says "No Rest for the Wicked." A possible reference to the song Ain't No Rest For The Wicked by Cage The Elephant.
Funny enough, the 2009 examine info said, "A big squirrel." In the 2010 event, the examine info says, "A cute, cuddly little squirrel...with teeth." It is commonly just thought that it's a mistake, if that's true, we might never find out.