Oooh that’s a good question! Idk if phobias count as “irrational,” per se, bc you can have an irrational fear of anything, but phobias at least have categories that are common? Right? 

These stories are open enough that you could make an argument for more than one irrational fear or phobia for each character, but for the sake of brevity I’m going to focus on one or a few for each, and keep my support brief. 

(TBH I started drafting this and just one character got really lengthy, so I’ll do a series of them.)

1) Louis 

A) Claustrophobia – The fear of small spaces like elevators, small rooms and other enclosed spaces.

Canonically, the first one that comes to mind is Louis’ claustrophobia. Idk if Brad was aware of that character trait, but I see it in his face when Lestat closes him up for his first night in a coffin. He has his hand on the lid at first, and then lets it go kind of reluctantly I don’t have that giffed out so you’ll have to believe me on that.

“All my life I’d feared closed places. Born and bred in French houses with lofty ceilings and floorlength windows, I had a dread of being enclosed. I felt uncomfortable even in the confessional in church. It was a normal enough fear. And now I realized as I protested to Lestat, I did not actually feel this anymore. I was simply remembering it. Hanging on to it from habit, from a deficiency of ability to recognize my present and exhilarating freedom.” – Louis, IWTV

^And then post-trial at the Theatre des Vampires, he gets nailed into a coffin and walled up, UPSIDE-DOWN. It’s a bad time. It’s a pretty bad punishment on its own, probably a standard one for the TdV, but I can’t help but think they had some idea that this was one of Louis’ fears specifically that they read in his thoughts and capitalized on.

B) Atychiphobia – fear of failure, specifically re: a fear of confrontation/decisions, because it so often ends in the death or pain of those he loves, particularly Paul and Claudia.

There is a more elaborate meta post out there about this, and I can’t find it, anyone can reblog this and add the link. @wicked-felina​ and I were discussing Louis and his fear of confrontation/decisions last night, here’s what we came up with:

• Louis tends to refuse to engage, except when he physically has to fight people to save Lestat in TVL ❤
• Re: Paul, imagine you having a fight with a family member and mocking them (being confrontational) and then they die right in the middle of your argument, and you’re blamed for it, and you blame yourself for it ;A;
• Claudia wanted him to choose between her and Lestat, “Now’s time to end it, Louis.” And Lestat ends up dead ;A;
• And he has to stand by and watch Lestat (debatable, but I consider Lestat to be his lover at the time) be hurt, lay there suffering as he appears to die on the carpet, then Louis has to help Claudia finish him off. 

“The numbness which had protected me since the carriage left the Rue Royale threatened to lift and leave me flayed suddenly, staring, thinking: This is Lestat. This is all of transformation and mystery, dead, gone into eternal darkness.”

^This suggests to me, plus the pull he felt to go down with Lestat, that he absolutely cared for Lestat, more than just for what secrets he took with him in death ;A;

• Armand wanted him to choose between him and Claudia for him, and Claudia ends up dead ;A;

People really put Louis in terrible situations and he’s frozen with indecision. Anne Rice has compared him to Hamlet, there’s so much weight on whatever he chooses.

“ …`That passivity in me has been the core of it all, the real evil. That weakness, that refusal to compromise a fractured and stupid morality, that awful pride! For that, I let myself become the thing I am, when I knew it was wrong. For that, I let Claudia become the vampire she became, when I knew it was wrong. For that, I stood by and let her kill Lestat, when I knew that was wrong, the very thing that was her undoing. I lifted not a finger to prevent it. And Madeleine, Madeleine, I let her come to that, when I should never have made her a creature like ourselves. I knew that was wrong! Well, I tell you I am no longer that passive, weak creature that has spun evil from evil till the web is vast and thick while I remain its stultified victim. It’s over! I know now what I must do. And I warn you, for whatever mercy you’ve shown me in digging me out of that grave tonight where I would have died: Do not seek your cell in the Theatre des Vampires again. Do not go near it.’ ” – Louis, IWTV

C) Autophobia – fear of one’s self – Not sure if this is the right type of fear, but I would add that Louis’ fear of his own vampiric nature in IWTV was a thing, too. 

I never revealed to him half my powers, and with reason, because he shrank in guilt and self-loathing from using even half of his own. – Lestat, TVL

^It has to do with wanting to remain human, and exerting his vampiry gifts was a glaring reminder that he’s not; having grown up a Christian, he felt that being a vampire was monstrous and evil. This was something he struggled with more during IWTV-era than later, as we see in much later canon he uses his powers without explicit canon complaints about it. 

Louis has grown in canon, and he doesn’t seem to have these fears any longer, but we seldom know what’s going on with him as we don’t revisit his POV until the most recent books, and he doesn’t mention these things specifically. There’s probably still traces of them, though.