ed is well known for its consistent and user-friendly error interface.
ed user ends up having entered a bogus command,
ed will provide him a truly helpful and verbose error message, e.g:
help ? help me ? meep ? insert ? end ? exit ? quit ?
This can be pretty depressing, leaving the poor user alone and sad.
To cheer him up, I suppose the following modification:
/sys/src/cmd/ed.c:652, right before
putchr(L'o'); putchr(L'y'); putchr(L'o');
This will cheer up sad ed users.
I suppose that this variant shall be called