No Statler and Waldorf sets available yet, they will be available as single figures in Series 5 I believe, or possibly 6. There will be an exclusive Vaudeville style two pack available at Wizard World Chicago, for about 20 bucks. Collectors Club members are also allowed to order them. If you are still interested, contact me on or around Wizard World Chicago, and I will order you one when I order mine.
As for the others:
Kermit: Havent seen any in ages, keep your eye on Electronics Boutique or Toys R Us for the old exclusive Tux version which could possibly be around. Or hold out for less than a month, and Target will get an exclusive Koozebane Kermit, with a newsman styled Kermit in trenchcoat w/ mic, and a display base featuring Koozebanians and Murdelumps (sp?)
Animal: Can only get him in the Electric Mayhem set, or you can buy the convention tour edition that is sold at most conventions Palisades attends. You can buy it through the Collectors Club if you want to join ($50 life time membership)
Gonzo: Two were available, standard retail version and Electronics Boutique exclusive. Might still be available at ebworld.com
Rizzo: Just now shipping. Should show up in stores soon; Target will be carrying Muppet figures starting at Series 4 which includes Rizzo. Should be available at Target in a bit less than a month when they do the Toy Dept. resets. He's shipping to stores like Suncoast, Media Play, Sam Goody, and Electronics Boutique right now.
Hope that helps!