Nothing in Lighter. But I vote with Uncle Dave O and John Giok-- someone who can't vary his reactions but always follows the rules.

The Oxford English Dictionary:
Monkey, 1c: Monkey Up (or On) a Stick- A toy consisting of a monkey attached to a stick so that it can be moved up or down it on a sliding ring.
1863 Tyneside Songs: "In these days he was a regular brick,
When he seld the monkies up the stick."

Meaning of 'brick' in Tyneside language? Dunno.