Mungo P. Tannen was a warden of a prison in Sydney, Australia during 1790.
At some point during the year, two bank robber (Frankie and Sidney) from 1992, crashed into the prison after their arrival to the time period. As a result, Mungo arrested them and put them to work smashing rocks.
After catching Einstein returning to the DeLorean time machine, the two bank robbers ran from Mungo, prompting him to pursue them. He was unsuccessful as a kangaroo that Einstein befriended bounced a hammer onto Mungo, while Einstein got the Delorean running.