Don-Chan appears just as a regular Tanuki. As with it's owner, it's body proportions and appearanace can vary from game to game and even side media. As Tanuki are known to be gluttunous and opportunistic eaters Don-Chan can appear to be overweight in some appearances. To differentiate Don-Chan from other village Tanuki Don-Chan it usually (but not always) is seen with a ribbon or other accessory tied to it's tail, something Don-Chan doesn't seem to mind.
An interesting concept in Street Fighter Legends: Ibuki that is implied (but never stated) is that Ibuki is actually just closer to Don-Chan than other Tanuki rather than it being her pet. This is shown when Don-Chan isn't allowed to follow Ibuki when she was leaving the village. However it should be noted that said comic has inconsistencies with the main series such as Sarai not being a ninja and Ibuki learning Yoroitoshi (her strongest attack) when she battled Oro when in the games she had access to the attack since at least the Street Fighter IV series (that in canon takes place before Street Fighter III).Regardless of their relationship Ibuki is shown to care about Don-Chan. Don-Chan is shown to be the only one who Ibuki openly talks to about her grievances. She also tends to have Tanuki themed accessories in her alternate outfits. Ibuki's Street Fighter X Tekken swap costume even states she added a Tanuki tail solely as a reminder of Don-Chan. When everyone recieved Wild Animal outfits in Street Figher IV Ibuki's outfit was that of a giant Tanuki. In certain winquotes Ibuki talks about Don-Chan, such as her winquote against Yang in IV where she states that his hair reminds her of Don-Chan or when beating Toro in SFXT where she wishes Don-Chan could talk too.
Don-Chan also is shown to care for Ibuki back, he stood by his master during the whole trip and back during their trip of the Kazunuki Estate and never caused any trouble. In some side media Don-Chan is shown picking on Ibuki and even tickling her (a picture Omar Dogan would actually show in the future in his Deviantart page). Don-Chan also willingly was used as a distraction by Ibuki during her battle with C. Viper in Free Comic Book day's battle comic.
Not much is known of Don-Chan's past, aside from it meeting Ibuki when it was just a Tanuki pup. In modern days it is known for following Ibuki just about everywhere (even an airplane as shown in her Story Mode). Even in games such as Street Fighter X Tekken that doesn't feature Don-Chan in person characters like Cammy, Bob Richards and Jack-X all talk about Don-Chan as if it in the scene (with Jack-X even saying Don-Chan is sitting on Ibuki's shoulder after he defeats her). Don-Chan is the only known pet that appears alongside it's owner in the Street Fighter, as it accompanied Ibuki in most of her official SFIV era artwork.
While Don-Chan has never been seen fighting, it was present in battle in some stages of Street Fighter III: New Generation. Similar how Yun and Yang are present when the other brother is in battle. Most notably Don-Chan is present in Gill's stage, where lava is flying around and Don-Chan would be in danger.
While it is never shown, Don-Chan is said to be the only Tanuki in the Glade of Ninjas who knows actual Ninjutsu. It should be noted that when Yuta came to Ibuki's rescue in Street Fighter Legends: Ibuki Don-Chan was seen in the very frontlines of the "Raccoon Air Ambush". However it is not known if Don-Chan is a leader of the local Tanuki's or it wanted to save it's best friend. It also is said to hate cars.
- In real life Tanuki are actually poor choices of pets, as they are not domesticated in any way and haven't evolved to learn the advantage of living with humans as other common pets such as cats have.