Unfathomably stoned. Extremely high. On the cusp of non-functionality. To reach this level of intoxication is no easy feat - it takes hard work towards a solid, stony goal. This is, of course, a reference to Willie Nelson, one of the world's most notorious potheads. Willie Nelson himself has only been Willie Nelson'd a handful of times.
It took 11 4-gram blunts of Alaskan Thunderfuck, but by the time 5 o'clock rolled around, we were Willie Nelson'd.