this site it says that if you are making a one time gift, you shoudln't have to worry about it.
I want to design an item using a popular character. Can I?
Please be aware that characters, such as Mickey Mouse, Bugs Bunny, Barney and so on, may be protected not only by the copyright on their image, but also by trademark registration. Use of a registered character can lead to problems, because the owner of the character has the right to control all use of that character, including reproduction on knitted garments and especially in patterns.
If you want to produce a chart of a character, you should contact the owner of that character first to be sure you may do so. If you are doing a one-time sweater for a beloved child, then you are probably in the clear. But, if you post the pattern on a website or sell copies, then you need to get permission or you can be in trouble for using the character's image without a license.