Ruth and Esther

Ruth and Esther are the two fembots that wrestled in the petroleum oil as a Robanukah tradition during Robanukah 3010, even though they ended up wrestling for 500 million years. Apparently, as they wrestle, there becomes less and less oil, so that the oil doesn't last forever. Maybe Bender just assumed that, which would account for the oil lasting 500 million years.