Repetitivemundane action with no seemingly worthwhile end result or a job that is lowly, boring, thankless or done on autopilot with one's eyes closed figuratively.
Rather than respected or appreciated for their knowledge, David and Hugo were relegated to the night shift clicking the mouse for 12 hours.
A mouse with gigantic tits. A mouse is a small, brown, furry rodent - this type has a large pair of human breasts on it's chest (think Pamela Anderson meets Mrs Frisby).