I was watching this short video on little-known things about the original Metal Gear Solid, and you hear one of the lines that he changed--and a ton of players, myself included, probably never heard this particular line until now.
The "onion" line was not in the Japanese--and by extension, is not in the Twin Snakes version. One of the top comments on that video talks about additions like this being why he was fired. The story seems to track, as far as I can tell.
Later games stuck much more closely to the script. Maybe a little TOO closely, like MGS3's Volgin mumbling "Kuwabara, kuwabara..." even in English.
If only more creators had this kind of balls.
Though if anyone cares, here's an article on the localization, written by Blaustein himself. Archived, of course.
4kids stuff was mostly because US TV executives didn't realize American kids would enjoy Japanese cartoons with Japanese stories, plus the kinds of people they would have hired back then would have been much more talented than the people who get localization jobs now.