How do particles become entangled?

[RandallB]

MWI.

Actually I think using a “Ball” is an ok analogy as long as it isn’t performing any impossible tests on itself, like trying to decide if it’s really dead or not! Better than “Schrödinger's cat” anyway.

Looked in other parts of thread but couldn’t find MWI defined. What is MWI-like?
EDIT: Think I found it --- from MWT to "Immortality"
Not so we'd ever know.