With our apologies to all the Larry's out there (we don't know why Surly makes that name association) welcome to the fattest thing in cycling - the brand new Big Fat Larry tires. They measure a whopping 4.7" width on 100mm rims, which makes them the widest tires for a 'conventional' bicycle that we're aware of.
Although they were designed specifically for the upcoming Moonlander frameset, they will also fit in the frames and forks of the Pugsley and Mukluk. However, you'll have to space your crankset further outboard, or get a different fatbike specific crankset, and/or put up with some chain rub (ie. lose a few gears) to accomodate the wider rubber if you're not using the Moonlander frame.
We haven't tested these tires on the 65mm Large Marge rims yet but are told that they will work, though that combination won't produce quite as large an overall tire width, which we assume means less chain rub issue in, for instance, a Pugsley frame. We're going to try to test this out as soon as possible and post the results here. Stay tuned...