I searched ‘Adventure Time’ graphs on Google and Pinterest for ideas, then made up my own graphs to work with. They are 16x16 square graphs. I worked 2 rows of (US) double crochet per 1 row of squares on the graph to get it close to square. Half-double crochet would also be suitable to use for these graphs.
My squares turned out ever so slightly rectangle (at 31cm x 33cm approx. 12” x 13”- had I worked in hdc, they would have been square)….but that’s fine for what I’m using them for.

Solid granny squares could also be used as an alternative here - 1 square on the graph = 1 granny square. You can make them whatever size that you like.

Graphs may also be worked in C2C (corner-to-corner) method. Here are two tutorials to help with C2C and how to colour change;
https://www.youtube.com/watch?v=qq_5lflBMIg
https://www.youtube.com/watch?v=3mBI7_uTWPc

I started each row with a chainless starting dc - it produces a more even edge, but you can also begin your rows with the standard ch3 if you wish.
Here’s a link to a Moogly ‘how-to’;
http://www.mooglyblog.com/chainless-starting-double-crochet/
If you need help with how to colour change, go to YouTube and look up ‘Intarsia Crochet’ tutorials…there are a few to choose from there.

I have added pics of the charts that I made - they include a little group of colours at the bottom of the pic. Use those to help you match your yarn choices.

When working the odd numbered rows (1, 3, 5, etc)…the side facing you will be the right side of your work. Looking at the graph, your rows will be worked odd numbered rows from the R-L and the even rows copy what you did in the previous row - ie: Work Row 1, Row 2 will be the same as Row 1 but the order will be reversed. A tip - each stitch worked in the even rows will be the same as the stitch below it in the previous odd numbered row.

Finn can be made with or without his backpack straps. These instructions are for Finn with his straps. If you wish to work the other version without the straps, just work your first 6 rows in mid blue, then follow the instructions from Row 7.

Finn

Colours;
White
Light Flesh/Skin tone
Mid Blue
Green
Black

Using your mid blue, chain 51.
Row 1: Work 1dc in 4th ch from hook, then work 4 more dc’s in mid blue, 7green, 23mid blue, 7green, 6mid blue. (48dc’s + 3 starting ch = 49dc’s).
Rows 2-6: Work 6mid blue, 7green, 23mid blue, 7green, 6mid blue.
Rows 7 - 10: Work 49white.
Rows 11 & 12:Work 15white, 19skin, 15white.
Rows 13 & 14: Work 12white, 25skin, 12white.
Rows 15 & 16: Work 9white, 9skin, 13black, 9skin, 9white.
Rows 17 & 18: Work 6white, 9skin, 4black, 11skin, 4black, 9skin, 6white.
Rows 19 & 20: Work 6white, 37skin, 6white.
Rows 21 & 22: Work 6white, 6skin, 4black, 17skin, 4black, 6skin, 6white.
Rows 23 & 24: Work 9white, 31skin, 9white.
Rows 25 & 26: Work 12white, 25skin, 12white.
Rows 27 & 28: Work 15white, 19skin, 15white.
Rows 29-32: Work 49white.
Finish off, sew in ends.