Four years prior to the events of Mystery Room, Alfendi wore a dark gray suit and had his hair shorter.
During the game, Alfendi wears a striped blue and red sweater with a long white coat. He wears red and white sneakers on his feet. He seems to keep newspapers in his pockets all the time. He keeps a long dark blue coat (as shown in the cases select screen), but apparently only wears it if he's not working (shown during the credits of the game). His hair is neatly tied back into a low ponytail behind his neck. Being Placid the color resembles purple while being Potty the color is deep crimson.
Due to the events at Forbodium Castle, Alfendi has developed split personality disorder, which has lead to him having two personalities. His real personality is nicknamed "Potty Prof", who was believed to have been the personality Alfendi developed at Forbodium Castle. Sometimes personality change makes him feel unwell (as seen in Cases 2, 3 and 4).
When Potty Prof comes out, his hair turns dark red and covers the majority of his eyes. He also has a temper and is obsessed with criminals—the more gruesome and evil they are, the better for him. He first came out in Case 2 and has appeared in all the following cases after. Florence Sich advised Lucy that she should be safe if a criminal is around when Potty Prof is out, but to run when she is alone with him.
His second personality is nicknamed "Placid Prof", and was believed to be Alfendi's real personality for the majority of the game. When Placid Prof comes out his hair becomes lighter and falls back behind his ears. He is very laid back and calm but can become quite emotional sometimes.
Lucy refers to him as "Prof" due to him teaching her how to be an inspector. Alfendi finds it inappropriate due to his father being an actual professor.
His relationship with Lucy Baker is often questioned by many characters. At one point, Roscoe Strapping referred to him as "frigid Fendi".
It is mentioned in Alfendi's profile in Case 9 that he is 29 years old.
During the events of Mystery Room, it is mentioned on several occasions that Alfendi has a brother. It is unknown whether this is referring to an actual brother or to his two personalities.
As of now, his only known sibling are Katrielle Layton and Flora, however the latter is an adoptive sibling.
In Case 2, which was the first time Potty Prof came out in the course of the game, Lucy compares Alfendi's split personality to Jekyll and Hyde, which may be where the idea for his split personality disorder came from.