It is a phenomenon known by many names:
Time-Slips, Time-Warp or Temporal Displacements, Time Jumps, Time Travel, Time Fabric Ruptures, Time Ribbons-or Strings-or Yarn, Time Storms, Time Slippages, Time Tears, Alternate Realities, Dimensional Leap-Frogging, etc. The author lumps them all under the acronym TWIDDERS (a jumble of time/warp/displacement with a pinch of slip thrown in). By its spontaneous nature, a time-slip, or TWIDDER, is differentiated from someday-through-human-engineered-means time travel!
Wrapping our brains around much of the theory that may one day explain how TWIDDERS can occur is a mind-boggling proposition. It all begins with REALLY BIG THINGS and REALLY SMALL THINGS. And the physics that deal with each.
So, if we do indeed live in just one of multiple universes and time is an illusion and if in one of these realities Elvis never died and if wormholes assemble and dissemble randomly throughout our existence and can transport us either to an alternate there or other Now and if the atoms that make up our being are perfectly happy to participate in said travel, then might we unwittingly be part players in a moment from history and/or visitors to non-congruent locations? And if we can go there and back again, have others from elsewhere come unwittingly for brief visits to our universe?