I'm probably not the only one who lets kids "help" with opening minifigure packs, so I figured that I would post this for anyone else trying to figure out which checklist/code sheet came with which minifigure. I was searching for this info a few weeks ago and wasn't able to find it, and didn't have a big enough sample size yet at that point to figure it out.
If you are trying to match the checklist sheet (and code) to the correct minifigure from the set, you can use the number printed in the corner on the back of the checklist.
The numbers printed on the sheet don't correspond to the checklist number of the minifigure, but rather the order the names of the minifigures are listed in Lego's official descriptive text about the set.
The numbers for the ones I purchased from a Lego Store here in the US (with 122091-1 next to the printed number) are printed as 16 higher than the listed order (17 through 32, instead of 1 through 16) so you just need to subtract 16 for those.
The ones from the box I bought on eBay which appear to have originated in Europe (with 122091-3 next to the printed number), are printed 1 through 16.
If you've got a printed number of 33 or higher on your sheet, you may just need to keep subtracting 16 until you get to the 1-16 range.
Series 13 - identification numbers on checklist / code sheets
1 (or 17) = Galaxy Trooper (16/16)
2 (or 18) = Alien Trooper (07/16)
3 (or 19) = Evil Wizard (10/16)
4 (or 20) = Classic King (01/16)
5 (or 21) = Goblin (05/16)
6 (or 22) = Snake Charmer (04/16)
7 (or 23) = Lady Cyclops (15/16)
8 (or 24) = Paleontologist (06/16)
9 (or 25) = Carpenter (09/16)
10 (or 26) = Hot Dog Man (14/16)
11 (or 27) = Sheriff (02/16)
12 (or 28) = Samurai (12/16)
13 (or 29) = Disco Diva (13/16)
14 (or 30) = Fencer (11/16)
15 (or 31) = Unicorn Girl (03/16)
16 (or 32) = Egyptian Warrior (08/16)
The same pattern seems to hold true for the series 12 sheets I have handy, so you could most likely use the same method to match up the checklist/code sheets to the series 12 minifigures as well.
3 = Wizard (01/16)
8 = Hun Warrior (02/16)
21 (5) = Swashbuckler (13/16)
29 (13) = Prospector (08/16)
There you go.