These electronically based creatures are not native to this
universe. They appear to come from a world whose laws of
motion are radically different from ours.

Tron looked to his mate and pilot. "I'm going to check on
the beam connection, Yori. You two can keep a watch out for
grid bugs." Tron paced forward along the slender catwalk
that still seemed awfully insubstantial to Flynn, though he
knew it to be amazingly sturdy. He gazed after Tron, asking
himself what in the world a grid bug was, and hoping that the
beam connection -- to which he'd given no thought whatsoever
until this moment -- was healthy and sound."
[ Tron, novel by Brian Daley, story by Steven Lisberger ]