Here are some that I found in reading the string-pool from Knuth's TeX:
[Note that I included these from the actual file, so the one with 'can
fix can fix' below is what's actually there!]


(That makes 100 errors; please try again.)


You can now delete more, or insert, or whatever.


Sorry, I don't know how to help in this situation.
Maybe you should try asking a human?


Sorry, I already gave what help I could...


An error might have occurred before I noticed any problems.


``If all else fails, read the instructions.''


This can't happen.


I'm broken. Please show this to someone who can fix can fix


I can't go on meeting you like this.


One of your faux pas seems to have wounded me deeply...
in fact, I'm barely conscious. Please fix it and try again.


Interruption
You rang?


IMPOSSIBLE.

NONEXISTENT.

ETC.

BAD.


A funny symbol that I can't read has just been input.
Continue, and I'll forget that it ever happened.


I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.


I dddon't go any higher than filll.


Dimensions can be in units of em, ex, in, pt, pc,
cm, mm, dd, cc, bp, or sp; but yours is a new one!
I'll assume that you meant to say pt, for printer's points.

The early versions of TeX had this classic, which I believe the people at
Stanford even had printed on T-shirts:


	You can't do that in horizontal mode.