Some HOTD1 arcade cabinets spelled his last name as 'Rowgun.'
A strange later-game example in House Of The Dead 4 Special, while every other game has agreed on Rogan, if G gets a high score, on the stage result screen, he'll comment that he's "Better than Logan."
The Stoic: In House of the Dead 1, he's basically a robot.
Unexplained Recovery: You meet him at the beginning of House of the Dead 2, where's he's been seriously wounded and urges you to go on without him, seeming to suggest that it's a Back for the Dead situation for him. In the best ending, Rogan shows up out of nowhere to tell you he's fine, but even if that ending isn't canon, the fact that he's back in the third game certainly seals it.
Jerk with a Heart of Gold: For all the trash talk and swearing he does to everyone else, especially G, he has more of a heart than most would be led to believe. G points out that Isaac doesn't mean most of the things he says, hence why Isaac refuses to use the MF-word on Clement. What does G conclude? That Isaac sees G as a good friend. Of course, Isaac won't admit it.
It's Personal: She wants to avenge her little brother Jasper, and later Candi.
Revenge: Her motivation throughout the game. It's safe to say that her fate determined she failed to avenge both her brother and Candi.
Dr. Roy Curien
Big Bad: Of the first game (and also the third game).
Driven to Villainy: Implied in HOTD1, and explored in HOTD3. Curien was just a normal scientist trying to solve the world's problems, but his son's sudden illness prompted him to go all the way to the bottom of the barrel to try and cure him. It cost him his coworkers, and his sanity.
Curien's most powerful creation, which is a mutant with fire control and psychic powers. The fourth (and final) boss of the first game. It later serves as the fifth boss of the second game, and the second (and once again final) boss of The House of the Dead 4 Special.
Achilles' Heel: Its exposed spots. Specifically the right shin, left calf, right forearm, and left upper arm. Perhaps the only final boss in the series where despite the weak point being listed as 'unknown,' the weak point isn't blindingly obvious.
Pop Quiz: In The Typing of the Dead, he parodies the format that The Tower used three chapters ago, using questions with silly answers. This time all three answers to each question are considered correct, although they influence which of the Multiple Endings you get.
Curien's ultimate creation/transformation, it is a cybernetic monster surrounded by a metal ring. It manipulates electricity to fight. It's the final boss of The House of the Dead 3, and is actually Dr. Roy Curien himself.
A humanoid mutant armed with swords and a purple aura, which acts as a "test" of strength for Kate and James. When he dies, he wounds James with a shard of his body. He's a perfected model of The Magician, and the fifth boss of The House of the Dead 4.
Boom, Headshot: During his tornado attack, his head becomes a weak point. Lampshaded on the analysis window; while all other spots save for his chest are labeled "NO DAMAGE", his head is labeled "NO DAMAGE?" Yes, with a question mark.
Vocal Dissonance: Despite its towering and grotesque appearance, it has the soft, withered voice of an elderly man. Ironically, it's probably the only voice in House of the Dead 4 that doesn't sound cheesy.
The first boss in OVERKILL, he's Varla's quadriplegic younger brother, who has injected himself with a Psycho Serum in order to kill Papa Caesar, but got distracted by G and Issac, allowing Caesar to escape. Unfortunately, Jasper ends up so far gone that he can't tell ally from enemy, and ends up attacking G and Issac instead.
Exclusive for the Playstation 3 version, they're Varla Guns' fellow coworkers who borrowed Varla's bike before getting infected. Appears as a fat woman and a skinny woman. Chronologically the second boss fought in the PS3 version.
Another creation of Caesar, who's released in a hospital in order to kill G and Isaac. Appears as a zombie girl with a mutilated face and powerful screams. The second boss in OVERKILL (third if you count the PS3 version).
Mind Rape: Apparently, that's what she does when she screams.
She Was Right There All Along: You find her in a room in the dungeons of the Hospital, but if you're careful enough, you can spot her stalking you through the building and running away.
In the Director's Cut of the Playstation 3, she literally screams at both G and Isaac just when they get inside the hospital.
Nigel and Sebastian
A pair of circus freaks mutated by the virus, who are now feeding on corpses in the circus. Nigel is the large guy, while Sebastian is the tumor-like thing embedded in his belly. The third boss of OVERKILL (fourth in the PS3 version).
Clement Darling's mother, who was exposed to the compound and had her brain put in Varla's body. She mutates to a giant, grotesque monster which births smaller mutants from her oversized vagina. The seventh and final boss of OVERKILL (ninth and tenth if you count the playable "Missing Reel" in the PS3 version).
Guide Dang It: Only in the Director's Cut of the PS3 version; unless you paid attention to your surroundings, you wouldn't even know how to even damage Mother in the revealed "Missing Reel".
Body Horror: The greatest case so far, considering that hers used to be Varla's body.
Boss Rush: It was implied by G and Isaac that they had fought off Mother first before your real fight against her. Played straight in the Director's Cut of the PS3 version, where you get to experience it.
Final Boss: A two-form one...that has the first form cut out in a "Missing Reel".
Final Exam Boss: Set up as one in Typing. The prompt subverts this trope by instructing you to type anything "as long as you type like a motherfucker", meaning you can win simply by mashing "adsfadsfdasdsaf" and the like ad infinitum. However, you'll also get "Type words associated with (character)" prompts, and typing matching words will inflict a Critical Hit.
Finger Poke of Doom: She attacks by literally flicking you off, and also by flicking tires at you.