Let's see..."I claim to have memorized 10000 games."  Hm, turns out it's pretty easy.

ive memorised 10,000 games, all of them went 1.e4 e5 2.qh5 nc6 3.bc4 nf6 4.Qxf7#

The person who trained me to become a coach knows at least 100 games by heart. His FIDE rating has remained the same for the last 20 years, that is, 2200-2250. He can also tell you the colour of any square right away, play blind chess, play simuls for 12 hours, etc. The thing is, he did not start to do these stuff to improve his chess, but because he enjoyed doing them.

However, I've heard him say that sometimes while playing a game, he can recognise some patterns from the many games he has studied, and if this happens, he plays at GM level.

lol

Well...It's a transliteration of what he said, so there's no way we can be sure, Andy ;)

I won a couple with this