Walking with Superman: Day 282

It's been ninety days, so Superman's expecting his usual visitor from the 5th Dimension, even as he tours the Physical Measurement Laboratory at the National Institute of Standards and Technology in Gaithersburg, MD. The last thing he's expecting is a visit from five Misters Mxyzptlk! The little bald one in the purple suit has turned the lab upside-down trying to find someone named "McGurk," while the one with the cigar and the orange jumpsuit is busy fiddling with the fundamental constants of the universe, and the one with the buck tooth has rearranged the Periodic Table to spell out "NaMRePUS"! Meanwhile, the white-haired twins in the business suits are putting on a piece of performance art--using an Earth-shattering amount of antimatter! Superman's a little out of his depth on this one, so it's a good thing he has help--as a very annoyed modern Mxy lends an extradimensional hand!