Personality
In terms of personality, Fishy Boopkins' dad will always be hostile towards those who torture his sons. However, he can also be helpful, such as sending people to where they need to go. In SMG4: Mario goes to subway and purchases 1 tuna sub with extra mayo it could be implied that he has very little sense of justice, as he's willing to attack anyone who pisses him off regardless of whether he knows them or not unless his son begs him not to.
History
He is the father of Fishy Boopkins