Here's a dare & most probably the best babysitting dare you'll ever get: For the whole duration that you will be responsible of the child act as responsibly & maturely as possible & do everything possible not to break the trust that her parents are putting in you by letting you taking care of her in their absence.
Then when the parents are back & you're done with babysitting, do whatever dares you want.
Oh & I dare you also
not to do alexrules01 last dare in his post above... (that's what I meant anyway by not breaking the parents' trust). Running through the parents personal stuff isn't that great of an idea either, by the way...