Transcript follows. Image courtesy of original Roger Rabbit animator Peter Western. Huge thanks to Joe for bringing it to my attention.
Recommended reading: The Animator's Survival Kit: A Manual of Methods, Principles, and Formulas for Classical, Computer, Games, Stop Motion, and Internet Animators.

Transcript
AUGUST '87
MEMO TO ALL ANIMATORS, ALL ASSISTANTS, ALL INBETWEENERS
EYE LINES
A MAJOR PROBLEM HAS JUST LEPT OUT TO FACE US…
THE EYE LINES BETWEEN CARTOON CHARACTERS AND LIVE ACTION ONES ARE PROVING INCREDIBLY CRITICAL.
(NO WONDER MARY POPPINS WAS AWFUL IN THIS REGARD)
THE WHOLE TRICK IS BLOWN IF THE CARTOON PERSON DISCONNECTS HIMSELF FROM THE LIVE ACTORS EYELINE.
- IT SEEMS THAT ONLY 2 OR 3 FRAMES WRONG IS ALL THAT IS NEEDED TO BLOW THE ILLUSION.
THIS OBVIOUSLY HAS NEVER BEEN FACED OR SOLVED PROPERLY BEFORE AND SOMEHOW WE HAVE TO.
TAKE EXTRA CARE…
DICK