What, exactly, are Pi's myriad flaws? Are they flaws or just character traits or life outlook?

I think we need to come up with a list to debate.

Are they flaws or just character traits or life outlook?

I couldn't start to answer your question without knowing why those are mutually exclusive.

I'm hoping all this is leading up to building a stronger connection between Beckett and Alexis. We've had plenty of clues that Beckett declared her independence in all kinds of ways that her parents didn't approve of. She seems to understand that this is just Alexis trying to become her own person.

I don't think Castle is wrong because Pi is ridiculous and I don't think Alexis is wrong because, well... she's 19 and Pi isn't a bad person. I also don't think Pi will last too much longer because he is so very ridiculous.

Some of the things that Castle does not like about Pi are not necessarily character flaws, but just a very different outlook on life. These are the things that I can think of that count as potential warning signs for character flaws on Pi's part:

1. Whatever the heck happened to his passport/Amsterdam home. Now, there may be a genuinely innocent explanation, but it seems at best to indicate some flakiness.

2. Leaving his personal possessions strewn about such that Rick stepped on the business end of his belt buckle. While being a bit messy is hardly the worst sin, a little safety consciousness is a big virtue especially in someone else's home. (I say this as THE person who can never remember to shut cupboard doors.)

3. Not having a job when he met his girlfriend's dad. This could be a sign of a gold-digger. The facts that he has a very good reason to be between jobs, having just come back from Central America, and that he managed to get a new job fairly quickly may tell against it, but that does not take way the bad taste in the mouth from the first impression.

4. He is awfully New Agey, very surfer casual in how quickly he was ready to just crash on his girlfriend's couch. That is all outlook/personality. I mean, that is the part of him he has used most to contribute to the household - breakfast smoothies, Rei-ki. This seems to bother Castle as much as anything I consider to be a genuine problem.

Pi thinks spelling isn't important. This is a character flaw.

Wow, flaky and messy and not super considerate at 19.

We've seen all of that but also generally goodheartedness. Clueless, and intensely annoying to Castle? For sure. Not in line with his vision of Alexis? Absolutely. Worse than that? Not really. He needs to get over this shit.

It's the fruitarian thing that gets me the most. He's like the flip side to my post-college boyfriend's roommate who ate nothing but ramen for 2 months and ended up with scurvy. After that if someone mentioned ramen he'd shake his head and say, "Oh man, that stuff'll give you scurvy."

My parents would ban Pi from the house, and me dating him wouldn't even have to come into it. That's where I come at it from. Their house, their rules, and thing #1--you offer respect to the parents hosting you, and you adjust to their ways, or you leave.

They were clear about this when I was 12, and they were super duper clear when I was 19. The minute one of them got even mildly injured because he was treating their floor like his closet we would be encouraged to never speak of him to them again, and keep our socialising out of the house.

Castle was rude in their apartment, no question there (I'm trying to imagine my parents there, and it's nothing but laughs (at everyone's expense)), but if Pi wasn't respectful in his, is it an important part of Pi's social contract? 19 is plenty old enough to be respectful. And it's clear that Castle isn't used to disrespectful friends of Alexis.

So--even if he'd dislike him only because he's dating Alexis, I don't think there's a question that the writers chose to paint him as a buffoon, albeit one who wants to save the world.

The comments about Alexis being able to get an apartment ... isn't that pretty much standard for TV? especially shows about young people in New York (like "Friends" ... although I never really watched it). And I'm always reminded of the depression-era studio executive who complained that a character was looking too prosperous with something along the lines of, "she's a schoolteacher, she can't be making more than $300, $400 a week" (in the depths of the depression, mind you).

On Friends they actually made it clear that Monica was illegally subletting her Aunt (I think)'s place and Phoebe got her's from her grandmother. Chandler and Ross both had good jobs and Joey occasionally didn't pay rent.

I always appreciated that about that show.