Yes, I would say so. It’s an old-fashioned word, but it’s funny and I think it goes well with the character. It comes across as less harsh than “bitch” and “slut”.
What does Van Helsing mean by “serious” people/behaviour? Is that a quirky turn of phrase specific to him?
Exactly what I was hoping! Thanks a lot 
What does Van Helsing mean by “serious” people/behaviour? Is that a quirky turn of phrase specific to him?
Nope… I was in doubt if this was ok in English, and apparently it’s not. By “serious” I mean “reliable”, “dependable”, trustworthy, I guess… So , “a serious person” is not something that an English speaker would say? What is the common English way to say "reliable, dependable person, someone that takes matters seriously (I can’t seem to escape from using that word…) = that doesn’t fool around making jokes.
I suppose I could just replace “serious” with “reliable” in the text, but there must be a more common adjective…
Probably “trustworthy” would work… The meaning is correct… but to me it doesn’t sound like a word that would be used by someone who is enraged for having been let down… Or does it?
in other words:
“you let me down! You are not a _____ person”.
what would the English say in place of ____ ?
What about “honest”?
You can say a person is honest, and there is also the phrase “honest work”, which means a job where you have to work fairly hard (instead of earning money without any effort, or by shady means). Because of the second case, I think you could apply the word “honest” to other nouns with the same effect.
Wow, that 's a great suggestion 
it is a common word
it is a word that you would normally use to criticize someone , in some context
but in this context it’s inappropriate (which makes it funny).
Basically here we have the rant of a guy who is trying to criticize someone who outsmarted him. So we need a word that is common to criticize someone, but not in this case. Thank you!
Since you’re so good, I will ask you something else shortly
but if that’s the logic, we can also use “disappointing”. That’s not bad either…
“inadequate”… could be funny too. (though not common)
I think I might use “disappointing”. this way it sounds more like a tantrum of a child. It could be funnier…
Ok, here’s my next question. I have a character who in Italian is called “Scemo di guerra”, which literally means “fool of war”. this is a person who went to war and got injured to the brain and became stupid.
Now I assume in English there is no expression for that… I don’t think “war fool” is an expression? So I need to understand : Is it funnier to translate it with “war moron” , with “war fool”, or with “fool of war”, or something different?
The dialog is :
WAR MORON: “OI! You gals! Whatcha talkin bout?”
CAMILLA: My god! Who’s this one?
VILLAGERS: Don’t mind him, girls! He’s the war moron! He’s not dangerous!
OLIVIA: War moron? What on earth does that mean?
VILLAGERS: Just that! He’s one who went to war, and came back a moron!
OLIVIA. Oh.
CAMILLA: Excuse me, but shouldn’t you be calling him “war hero” then?
VILLAGERS: Er—yes. We probably should. But it’s too late now, girls! What’s done is done!
CAMILLA: what are you talking about? Can’t you just call him something else?
VILLAGERS: it’s done, girls! What’s done is done! There’s nothing we can do about it, you know!
[…]
Yeah, “disappointing” is funnier, especially when it’s used in every sentence 
Agh, I can’t think of anything! I’m afraid that question is too challenging for me, sorry! 
.
Btw, https://en.wikipedia.org/wiki/Madman_at_War
How about something like “shellshocked”? (Or in modern terms, PTSD.)
How did you find that?
However, in that translateion they gave another sense to the expression … they made it become “someone who behaves like a madman while at war”. that won’t work for me…
Well… can’t use it… whatever it is, it must contain an insult…
How about a neologism? It allows the player to experience the same wonder over what it means as the girls do.
The warnut - what’s that?
He went to war and came back a nut!
For an alternative for Serious/disappointing/honest/non-reliable, I’d go with “fickle”. Or in the context of Van Helsing’s reaction, “wayward” may be even better suited (as if the whole town is in on it and is deliberately stealing his thunder)
I searched for it, that’s all. Movies can be wondrous sometimes. 
I also looked for it on LT, but that book title doesn’t seem to have any translations: Editions: Storie di uno scemo di guerra by Ascanio Celestini | LibraryThing
“came back nutty” is probably more idiomatic?
He went to war and a bullet cracked his skull like a nut. That’s all he is now.
Nice but sounds too polite… I don’t see the improvement over “war moron”…
For an alternative for Serious/disappointing/honest/non-reliable, I’d go with “fickle”. Or in the context of Van Helsing’s reaction, “wayward” may be even better suited (as if the whole town is in on it and is deliberately stealing his thunder)
How do you know these strange words? Unfortunately I’ve never heard them, so they don’t communicate anything to me I think they’re too sophisticated for that reason… I can’t be understood only by native speakers…
(which applies to “trollop” as well, actually… 
)
Exactly!!
Fickle made it into the Collins Cobuild Advanced Learner’s Dictionary (albeit as one of the less frequent words); trollop did not.
Fickle occurs 1425 times in COCA (Corpus of Contemporary American English), trollop only 96 times.
Fickle means you’re likely to change your mind, basically untrustworthy without malicious intent. It’s not that unusual imo.
Also, Google n-grams.
Plus it’s a word I could hear Friends’ Ross repeat over and over in a high-pitched voice when he goes in overdrive “FIIIICKLE!”
And for the lesser-literates, they might associate it with that other F-word, which could be funny too.
But you’ll admit that trollop has something funny about it, even when you don’t understand what it means 
Yes, I do like fickle. It does sound funny even when you don’t know what it means… only, I’m not sure I like it more than “disappointing” …
Try reading the text out loud, with the right amount of anger and see which one feels or flows more natural. Shorter words win (imo)