Snap Roll.

I can't find the maneuver as it was depicted in the show either in my
Aerobat manual or in Neil William's book.

The snap roll in the Aerobat manual is what I was thinking of when
Bertie mentioned snap roll -- essentially an accelerated spin in the
direction of flight which involves inversion about the longitudinal
axis. Maybe there are other versions of snap rolls that don't "invert"
you about the longitudinal axis. I dunno.

Let me describe the P51 maneuver this way: Imagine a car driving along
a gentle curve being chased by another car -- the first car hits a
patch of ice and does a rapid 360, recovering in the same direction as
it started.

That's pretty much what the plane did (although it climbed some during
whatever kind of stall this was). Anyway now imagine the headlights of
the spinning car are machine guns: as the spinning car gets to about
270 degrees from original heading and the chasing car is starting to
go past the guns start to fire, continuing to fire as the first car
spins back to its orginal heading, nailing the second car the whole
way as it goes by.

The P51 was never "upside down" as you'd expect in a snap roll. Maybe
a spin out?

Bang -- down went the 109.

Speaking of airframes coming apart, I don't recall ever reading about
such things happening in WWII dogfights. It seems it would given the
complexity and fear of the situation. Did it happen much? Maybe that
kind of thing wasn't reported because it's not exactly a heroic end to
an aircraft / pilot.

I understand disintegration was far more common in WWI.