Barkis is willing informal
If you say that Barkis is willing, you mean that you are willing to do something.
A: "Are you ready for tomorrow's presentation?" B: "Oh! Barkis is willing!"
Boss: "Are you willing to face difficulties?” Jane: “Barkis is willing.”
To be ready for something to happen
The expression "Barkis is willing" first appeared in Charles Dickens' well-known classic "David Copperfield". Barkis is the name of a character in the novel who used this phrase to propose to Clara Peggotty, the maid of David's mother.
Children or adults often say this phrase to get their friends to join in something, especially to jump into a swimming pool (pond, lake, etc.)
“Last one in is a rotten egg!” yelled Jane, jumping into the pool.