piffy on a rock bun

Etymology
Age and etymology are uncertain; it existed in the 1930s and possibly derives from a music hall catchphrase. Some commentators (e.g. World Wide Words) suggest that piffy may have originally been patience, and the rock bun was simply a type of cake.

Noun

 * 1)  A person ignored or sidelined from an activity
 * I hate your work parties: you always talk shop with your mates and leave me sat like piffy on a rock bun.

Usage notes
Common in North-West England, sometimes shortened to just like piffy. It is the Northern equivalent of the Southern like a lemon.