MARTEN: "What is it that you find difficult about (drawing) Mimi?"
WATCHER: "I can't seem to get her legs drawn right. Also I want to draw her in your style"
Well, given Mimi is a character I've adopted into my official universe, I don't think a 'Mimi style sheet' too much to ask of me.
Most of the proceeding observations will be of the anime (original) version of the character (the guide's useful to more artists this way).
I should say I know very little about cartooning (as if my art didn't testify to that already). For example, a single pencil mark by Chuck Jones would carry more weight, and convey more intent and dexterity than everything in my gallery combined. ^^
That said, I'm not a complete idiot (I'm never completely good at anything, including idiocy), so I do know a few things ...and these are they!
When one wants to draw a TV character, the first thing to do is gather references. Expressed in a way that sounds less like work: just watch cartoons featuring the character.
In Mimi's case, the show is AotLK, of which YouTube is a great resource. Watch for odd angles and the like of the character; make a few screen shots (preferably those that show the character at eye level and in full-body), and take some notes on how the character moves, etc.
After, the screen shots should be trimmed to focus on the character.
Now comes the fun part: just stare at the character a while. Break the subject down into component parts, taking care to observe the respective sizes and shapes or the various parts (esp. of the head and torso).
In Mimi's case, her head is just a modified circle and her body a modified teardrop.
It must be stated that animated cartoons are drawn by many hands. That is, a given subject may appear slightly differently when drawn by multiple artists (even within a single episode!).
As examples, I've observed variations in Mimi's width, as well in the sizes of her eyes and the degree of curvature (or lack thereof) of her cheeks (among other things).
So, there are no 'absolutes' where drawing Mimi is concerned. An artist may perfectly depict Mimi as she appears in (say) Episode 11, but the drawing will not perfectly match the Mimi in (say) Episode 14 (the same applies to most non-Disney characters).
In other words, the goal here isn't to draw Mimi on-model, since no 'absolute' interpretation of Mimi exists (including my own). Just draw Mimi as seems fitting/as appeals to your eye.
First, Mimi's general proportions must be determined (ie, the character has to be measured).
Most cartoon characters made for animation are measured in terms of head heights (HH), so the question is how many 'Mimi heads' would it take to equal her total body height (not including her ears)?
The answer is 2-1/2. Mimi's head = 1 HH (duh!), her *torso = 1 HH, and her legs - 1/2 a HH.
*Mimi's torso is defined as the extent from the base of her head to the bottom of her skirt/'bit' area.
How 'high' should Mimi's head be? And, for that matter, how wide?
Heads, generally, are measured by the height and width of their eyes. In Mimi's case (presuming she's looking directly at the viewer), it appears Mimi's head is approximately 3 vertical eyes high (from the center) and roughly 6 horizontal eyes wide (cheek-to-cheek).
The 'eye width' of Mimi's head will increase if she were to turn her head to (say) a 3/4 angle.
To repeat, Mimi's proportions will vary. Moreover (again), some artists will draw Mimi's eyes bigger or smaller than other artists, without necessarily adhering to the numbers I cited above.
A given artist, therefore, has to decide how they want their 'Mimi' to look, and adjust the numbers/proportions accordingly.
For myself, I prefer drawing Mimi with larger eyes---eyes are windows to the soul, after all, and the soul needs all the light it can get (esp. given how dark one's mind can be). :3
I was told, specifically, the one who suggested this reference had difficulty drawing Mimi's legs. I'm unsure what the difficulty could be, but I will say Mimi has very short legs (as do most of the AotLK characters). Consequently, the characters are limited in the ways they can stretch, bend or cross their legs (and arms, for that matter).
As for my version of Mimi, mine is drawn slimmer, with a greater taper to her arms and legs. this is so she'll fit visually in the world of Gene and friends (it's also easier for me as I don't need to remember too many specifics when making quickies/comics). ^^
https://www.deviantart.com/martenferret/art/Mimi-Guideposts-and-Observations-Not-a-Tutorial-846220068
I have a little storenvy store open now! Check it out! 
