Possible Clues:

• Schoolboy joke?
• The little beast I had in the end
• Young animal
• Word that's missing from 20-, 26-, 48- and 59-Across and 9- and 39-Down
• ''Here's looking at you, ___''
• ''Here's looking at you'' ender
• Put on
• Billy the ___
• Farm youngster
• Just a little half of 19 across