The term 'Pen Denizen' can refer to a variety of different people, including a FELON (5 letters), CON (3 letters), BOAR (4 letters), PIGLET (6 letters), and RELIEVER (8 letters). A FELON is someone who has been convicted of a serious crime, while a CON is a person who engages in fraudulent activities. A BOAR is an adult male wild pig, while a PIGLET is a young pig. Finally, a RELIEVER is someone who provides relief or assistance in a particular situation. All of these terms can be used to describe people who inhabit a pen, such as a prison or a pigsty.