Yes, No Vowels was the one. It was on the CD that came with Macintosh Revelations, a very good book from the mid 1990s.

nVIR was indeed the one that said "don't panic" but I believe it also was a RAM and resource hog. And yes, it was widespread and came in a bunch of strains.

There was also an AfterDark 3.0 module that did a DOS prompt. If I recall it even typed in format c: from time to time...