When Bobby Fischer learned from Erwin Nievergelt

Erwin Nievergelt, a Swiss chess player, lost almost all games in the 1959 Zurich chess tourney, finishing shared last with 2.5 points out of 15 games. Bobby Fischer finished shared third with 10.5 points out of 15 games. However, Nievergelt played an epic game versus Paul Keres with a remarkable setup : castle short, play g4 with rooks on g1 and g3, and it is likely that Fischer noticed that game in the tourney bulletin :

In 1970 Bobby Fischer played a game versus a young Ulf Andersson, and we see the same manoeuvre.
(Note : After the game Ulf Andersson was so impressed with the hedgehog setup that Fischer played that he started to play and advocate it himself, and later went on to win against the, then brand new world champion, Anatoly Karpov.)

Later, the manoeuvre was used by other chess players, for example by Magnus Carlsen in 2022. Note the very close similarity with the Fischer-Andersson game [1] :

And Artur Yusupov :

Fischer also played the idea in 1966 :

Much earlier, in 1877, the idea was already used by Louis Paulsen :

Epilogue :
It is fair to mention that despite the poor result in the 1959 tourney, Nievergelt did very well in the earlier 1954 Zurich tourney where he finished second with 8 points out of 11 games, and ahead of former world champion Max Euwe. Nievergelt also won the Swiss championship several times.

I'd like to give IM Gert Ligterink some credit for this story as I read about this in his weekly newspaper chess column, many years ago.

[1] Magnus Carlsen on Bobby Fischer at wikiquote :

What I admired most about him was his ability to make what was in fact so difficult look easy to us. I try to emulate him. ~ Magnus Carlsen