The Costume: 'Up' odd couple of elderly grump Carl Fredricksen and Wilderness Explorer Russell
What You'll Need: For Carl: high-waisted, dark brown pants (try these from Wal-Mart), white dress shirt with cuffs rolled up (Sears), suspenders (Amazon), tweed jacket (try your local vintage store), glasses (Amazon), newspaper, helium balloons (Balloon Time), perpetual scowl.
For Russell: It isn't a real organization (sorry, kids), but you can make Russell's Wilderness Explorer costume by combining a yellow shirt, orange scarf, brown shorts, yellow cap, brown sash (with all the badges except the Assisting the Elderly one) and binoculars -- or, if you're not quite as industrious as Russell, you can buy the t-shirt at the U.S. Disney store, or the entire costume at the UK Disney Store. Don't forget the alarmingly sunny disposition.
Optional Accessories: If you've already got a golden retriever -- or any similarly colored mutt -- who can pose as the faithful Dug, you've got it made. Otherwise, you can purchase the stuffed animal version, which will be less hyper than the real thing, but likely a tad more obedient.