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(Fr that's pretty interesting)

Her hair was black in the first movie

I guess hair colour is changable, I once had blonde hair when I was a few months old

She probably dyed it.

My hair was black when I was born, but it is brown now

i mean it’s possible her hair changed colors over the years or dyed it...

Yes

The Toy Story series started in 1995, latest release 2019.
Andy is 17 and I’m not certain who the other girl’s age is.
Mrs. Davis, Andy’s mother, is at least 3 decades old.

The Monsters series started in 2001, latest release 2013.
Boo is 2 years old.
Monsters Inc. took place in a different universe.

So no, Boo did NOT grow up to be Andy’s mother, as there actually is no such thing as universal travel in the real world.

Yes but, this is Pixar/Disney we are talking about. In those universes, anything could happen. Depending on how old Andy is in the first toy story, which looks like between 5 and 12, most likely 8 and if you say Mrs Davis must be 3 decades old at that time, there is still a possibility as Boo was about 2 or 3 years old, so in 27 years, a lot could change and Boo could have well been Mrs Davis.

However, I can agree that they are parallel universes but that is a theory for another day. Another reason it may not be Mrs Davis is because Pixar is the king of Easter Eggs so Jessie may have only been an Easter egg.

Damn looks like we both snorted the Smort Cocaine, didn’t we

Or the Smort juice.

This is big think time

Ah yes, conspiracies

But hey! That’s just a theory, a game theory!