"leave immediately, sooner if possible"

In the series Shameless.US, S06E10, an actress utters "leave immediately, sooner if possible". Is this idiomatic? I'd like to know why sooner refers to.

Solution 1:

It isn't quite idiomatic, although there are plenty of similar expressions.

It's just humor.

Clearly one cannot leave sooner than immediately.

Some experts assert that Franz Liszt's legacy includes a piano score with the author's note at the top of each page, and those notes progress as follows:

Page 1: "Play very fast." Page 2: "Play faster." Page 3: "Play even faster." Page 4: "Play as fast as possible." Page 5: "Play faster still."