Shampoodle
Shampoodle is a hair salon run by Harriet who appears again from the previous games. It is the only place you can go to get your hairstyle, hair colour, eye colour and mii mask changed. In order to unlock Shampoodle you have to have had Kicks/Shoe Shank open for 7 days and spent more than 7,000 bells at the Able Sisters and Kicks/Shoe Shank. It takes 3,000 bells to take a hair cut, change eye colour and put on a mii mask. You can do only one of these once a day. To get a completely random hairstyle: put the slider to "formal", tap "private", then tap "doesn't matter".
Once Shampoodle has been open for two weeks and you have changed your hairstyle at least once, she will upgrade her machine to change the color of your eyes with contacts (see: Eye Guide) and will begin offering the haircuts of the opposite gender.