Monsters that look suspiciously like genitalia can resemble either male of female genitalia. The degree of resemblance required to classify a monster as such depends mainly on the imagination (or depravity) of the mind of the player.
The design choices behind these monsters vary with the game and the developers. In the case of the Shin Megami Tensei
series, monsters such as Mara
were designed specifically to look like a penis
, because these monsters are related to sexual deities
. In other case, such as with The Destroyer
, the resemblance is more accidental.