Friends:
People that fall under this category have successfully managed to pass Porky's extremely high standards and become what he truly can consider a friend. Either that, or they are just as immature as he is/put up with him. Chances are, he'll be more than happy to help them out, which is really saying something, considering how much of a prick Porky actually is.
Harley Quinn: Porky's first friend at the institute and quite possibly Porky's first friend period. Unlike most people here, Porky can be immature and goofy around Harley, which is pretty therapeutic after having to act like some stuffy adult in front of everyone else. Plus, Harley isn't critical of him, and since being insecure is what basically drove him to attempt global genocide, that's a big deal.
Associates:
People that Porky thinks of as associates are people that generally don't annoy him, but aren't really nice enough to him to be considered a pal. Given that Porky's mood fluctuates rather often, people that hate him could be considered associates by him. He probably won't do much to help them unless they ask for it specifically and definitely won't help them if it's dangerous in any way.
Evangeline McDowell: Evangeline seemed like nothing more than a little girl with strange tastes when she and Porky first met, but he soon developed a kinship with her, as they're both villains. Since Porky has to downplay the omnicidal maniac part of him most of the time, he values the rare instances where he can just be a villain. In many cases, that's when he's around Evangeline. Plus, she sucks at chess, and if there's one thing Porky loves, it's winning.
Raine Sage: The ying to Harley's yang, Raine appeals to the scholar in Porky, which barely exists. The main thing that Porky likes about her is that she thinks that most of the things he has to say are interesting. It doesn't really matter what they're talking about specifically. As long as Raine keeps on stoking Porky's ego, albeit inadvertently, he'll be more than happy to chat with her.
Alita Forland/Falis: Even though she was pretty annoying when they first met, she still played with Porky, even for a little bit. In any case, she's an alright person in Porky's book. A bit loud-mouthed and pretty rough around the edges, but a good person at heart. If possible, he'd like to duke it out with her. Most of their first meeting consisted of trash talking, so he'd like very much to see who's actually stronger.
Jason Todd: Similarly to Alita, Porky befriended Jason after a little bit of trash-talking. After the mood lightened a little, however, Porky began telling stories about how he had survived the night in Doyleton and pretty soon he and Jason were planning on lighting the institute on fire. Ironically, Porky and Jason's relationship resembles Porky's friendship with Harley.
Neutral:
What else is there to say, really? Porky's met them, but he doesn't hate them or like them particularly. He might enjoy a chat with them or something, but that's about it, really.
Methos: An odd bird, to say the least. He was obviously hiding something when they met, but refused to tell Porky, which only made him more interested in Methos. One interesting thing that Methos did tell Porky, however, was that they came from different worlds and different time periods. All in all, he's a very pleasant, boring person to talk to.
Indiana Jones: Indy complimented Porky, which automatically raised him to some significance as far as Porky's concerned. Besides that, however, there isn't much of note. He managed to solve Porky's riddles, so he won a torch. Indy's probably on the neutral-associate border.
Hokuto Sumeragi: One on hand, Hokuto helped Porky when he was zombified and trying to eat her and Hitsugaya. On the other hand, she helped him by knocking him out with a bottle. The two actions sort of evened each other out. Hokuto's also girlfriends with Falis, so she's probably an alright person. Porky just doesn't know her too well, is all.
Toshiro Hitsugaya: Seemed like a pretty smart kid when they first met. Didn't lose his cool when zombies attacked, which is really saying something. Hitsugaya's also a shinigami, which is particularly interesting, considering Porky had never heard of them before. Other than that, he's perfectly neutral to Porky.
Enemies:
Woe to those on this list. Porky never forgives and he never forgets, so anyone listed here can expect harsh and brutal revenge in the future.
Lelouch Lamperouge: Given that Porky's plans for world institute-wide domination have fallen through, he is not nearly as mad at Lelouch as he once was. Plus, Lelouch has cemented his own reputation as a helpful person, so any attacks against him would probably do more harm than help to Porky in the long run.
Suzaku Kururugi: Given that the only reason Porky didn't like Suzaku was because Porky didn't like Lelouch, there isn't much reason for Porky to still dislike Suzaku. It's not like Porky needs a reason, however, which is why Suzaku is still considered an enemy.
Scott Pilgrim: Out of the hundreds of "patients" at the institute, only two of them know about Porky's past. One of them is Porky, which is rather obvious. The other, however, is Scott Pilgrim. Porky doesn't know much about him, but he is willing to do anything to ensure his silence.
Mysterious Red Pen Asshole/Haseo: During one of Porky's attempts to get some dirt on Lelouch, Haseo decided to call Porky a pedophile, which spread like wildfire. Although no one technically knows that it was Porky whom everyone was calling a pedo and Porky doesn't know that Haseo was the one to start the rumor, he's still pretty pissed off at him.