Wrist cuff manuals held the step-by-step procedures for each of the astronauts’ extra-vehicular excursions. Ernie Reyes, chief of pre-flight operations for NASA back on Earth, spiced up the checklists with little “Snoopy” cartoons. Snoopy, from Peanuts, was an unofficial mascot of the Apollo program (their black and white radio caps were named after the dog). 

More here: http://www.hq.nasa.gov/office/pao/History/alsj/a12/