When I was around 12 years old I used to play a snes soccer game. I played the Japanese version. By that time I didn't know any Japanese and had no intention to learn it.
I remember memorizing the words the narrator spoke. One of them, I still remember, was "????teshimata". It happened whenever I tried to do a long pass and missed miserably.
It sticked in my mind so hard, that whenever something bad happened in my real life, I would repeat the phrase as an inside joke while talking to friends who played the game with me.
Now here I am, 40 years old, finding out that 32 years ago I already "knew" what てしまう means way before I even dreamed about learning Japanese.
good story! 