Well for TW I needed something to represent the wolfed out form as well as the human form. There's a noticeable difference in fighting prowess and athletic ability when wolfed out. So for Alphas I have them with Inhuman everything normally going up to Superhuman when shifted. Catch is Wolfsbane and Silver (between the Argent name and incorporating Supernatural, it seemed best.) I figure betas just get claws and Supernatural Toughness/Recovery when shifted with the added Catch of "Alpha Wounds"
As for Buffy, that show wasn't one of the ones that made the short list of being characters the PC's knew, since it wasn't really a favorite. Instead of doing the first story, guest star, etc. phases, since it was a mother and son team, it made more sense (and gave more of a world building opportunity) to have a guest episode in each of three shows. So they investigated the Beacon Hills attacks, arriving after it was solved and finding out not all werewolves are evil; then they crossed paths with the Winchesters when the wizard/son got possessed and went on a rampage; finally they tracked a "vampire" across the border to find out it was a blood drinking Fae, learning about faeries from Lost Girl cast. Mystic Falls has been discussed in world creation, but the party hasn't been there. My main concerns as GM with Buffy are timeline and importance. The TW pack is just one pack of werewolves. Sam and Dean have saved the world, but their moment of being the only thing that matters is over. Now they're just hunters... with a pet angel. And Bo from Lost Girl is unique for not being aligned, but the idea has spread making Wildfae more common, but with the risks being as they are, not that much so. Buffy seems different. Since she's the chosen one with all kinds of supernatural strength and the target of every baddy ever, I worry that'd draw the focus from the party. Then there's the fact that Sunnydale was destroyed in 2004 and Los Angeles went to Hell in 2005, so that'd be some serious issues to deal with. So, if the party shows an interest in Buffy I might figure something out... but not right now. The rest are easier to mix in. Another show that will be added (the party doesn't know) is Haven. I'm going to have them need a particular troubled person's power, and then have to deal with Haven thinking they're the only town with supernatural stuff while the party deal with (and considering our group, mock) the stupid townies who can't control their magic.
I'm starting Submerged, but growing quick. Wizard (both character and player) is obsessed with the Fae, and likes the idea of the trouble he could get in with Unseelie Magic. Since I like the idea, I'm giving 2 refresh across the board so he's still playable. The huntress likes the fate points, and since she's got a ton of stunts, more's nice.
Between Supernatural being a favorite show among the group (we're total fanboys/girls) and the fact that the characters are Campbells, we didn't do City Creation, instead doing campaign creation. Some of our locations are cities. Physically, they're heading back from Canada and stopped in New York for supplies, figuring a major city would have some of the more obscure Catch requirements and magic supplies. Which is when Maeve is going to claim Manhattan, starting with freezing the Hudson and East Rivers and wrecking the bridges... including the Brooklyn Bridge the party is crossing.