From Mirror.Co.UK:

EXCLUSIVE: THE REAL MRS DOUBTFIRE, Man dressed as woman to nanny kids

A MAN posed as a real-life Mrs Doubtfire for FIVE years - dressing up as a woman to look after a couple’s two children.

But “Erica” Sadowski’s cover was blown when he disappeared with the youngsters and was arrested after a former college friend recognised him from a wanted poster.

(more here)

So…  Why do this?