Raymond Chen:

Tony Krueger is remembered in Wikipedia as the person who ported the game Chip’s Challenge to Windows for the Windows Entertainment Pack. But that’s probably not the code he wrote that touched the most people.

Tony worked on Word 1.0, 1.1, 2.0, then on Word for OS/2 and Word for Mac, then returned to Word 6.0 and several versions beyond that. He probably holds the record for “most versions of Word shipped.”

[…]

Tony made the spell checker much more unobtrusive so that it didn’t interfere with your foreground work. And when it found a problem, instead of waiting for you to trigger a spell check, it immediately drew red squiggles under potentially-misspelled words (and later green squiggles under potential grammatical errors).

Update (2026-06-30): See also: Marcin Wichary and Jon Snader.