Oh man, phases and me...
Well, when I was young like 1-5 I maintained two obvious phases. The first was my "Lion King" phase. I owned pretty much all the merch possible, had a bed spread, had the computer games, had all the action figures, and I watched it pretty much every day. This was the strongest expression of what could be considered my disney phase which lasted until I was about 10.
The other phase was the horses phase...I haven't really outgrown it, I just no longer find playing with plastic horses nearly as fun. (Please note, that is not to say I don't still derive some pleasure from this activity.) My grandfather built me a really nice small wooden stable to play with, I still own an obnoxious amount of stuffed and/or plastic horses. I read only books about horses, took riding lessons, and just generally still have an obnoxious level of knowledge about horses.
From 5-10 I didn't really have any particular phases other than I seem to recall feeling that the only proper color for me to wear was hot pink/ rose red. Cannot explain it, but I remember that happening and my mother encouraging this deranged belief.
Around ten I decided that I was going to be a chef and so I spent a lot of time reading cook books and cooking. Although that desire did eventually fade around the time I became a teenager, I still retain the skills she developed making me quite good at cooking and I still enjoy it as a hobby to this day.
Also around ten, I kinda started my tomboy phase which was essentially made up of wearing a backwards hat, jeans, and only playing with boys. (The latter was caused by me moving away from my two childhood girlfriends and there being no girls in my neighborhood.) This carried on well into my teenage years and a common mode of dress for me was wearing a sundress with jeans on underneath and a backwards hat. (I also had hair down to the small of my back so...kinda sending mixed messages there).
In my teenage years I wouldn't say I really had very recognizable phases. The only things which come to mind were wearing fingerless gloves and wearing tights with high boots and shorts in winter...but I still do that so I don't really see that as a phase. I feel like I was a strangely stable teenager in the sense that I think by then I'd figured out I was going to be a nerdy bookworm who was a huge gamer and geek.
Around my first year of college, I got heavy into the punk and emo scene which led me to developing an interest in hair. Over a year and a half I did every hair colour found in the rainbow and nature. I also learned to cut, style, dye, and bleach hair using youtube, the internet, and my own head for practice and education. I still cut the hair for pretty much everyone in my family and I'm quite good at it. The punk style of dress has pretty much stuck although I've since combined it with some bohemian and 1950s fashion to reach what I consider to be "my look".
I guess the cool thing about my phases is that none of them ever truly died out and in many cases led to me developing useful lifelong skills.