Understudies

In a ballet performance of Jack and The Beanstalk that I was involved in, the cast and understudies were as follows:

Character	Dancer	Understudy
Jack	Taylor	Lea
Mother	Jaime	Lauren
Cow	Lilani	None designated
Gypsy	Megan	Sarah
Vendor	Deedee	Jennifer
Imp 1	Lilani	DeeDee
Imp 2	Sarah	DeeDee
Duck	Alayna	Lilani
Flute	Lea	Megan
Giant	Jennifer	Taylor
Narrator	Lauren	None designated

Given the arrangement of the understudies and what parts are on at the same time, here's what could happen if a single person could not perform:

Taylor: Lea becomes Jack.; Megan becomes Flute.
Jaime: Lauren becomes Mother.; Someone becomes narrator.
Lilani: Deedee becomes an Imp; Somebody becomes Cow. (A simple part performable by anyone small enough to fit into the costume.)
Megan: Sarah becomes Gypsy.
Deedee: Jennifer becomes Vendor.
Sarah: Deedee becomes an Imp.
Alayna: Lilani becomes Duck.; Deedee becomes an Imp.
Lea: Megan becomes Flute.
Jennifer: Taylor becomes Giant.; Lea becomes Jack.; Megan becomes Flute.

Why couldn't Megan just replace Jennifer? Don't ask me. It's not a complicated part. Maybe she was too small, but I think she was taller than Taylor at the time.

I don't even want to think about what would happen if two people got sick. (Lilani+Sarah, Alayna+Sarah, or Alayna+DeeDee would mean they would only have one imp.)