I used to like pretending to be my characters talking on audiocassette, doing different voices; I had a big collection of tapes going back years. (Lost and likely damaged/corrupted beyond hope by now, alas.) At least one improvised conversation led into a novel I later wrote.
I disliked dolls (humans repelled me...even most of the characters I pretended to be were animals), but I loved collecting stuffed toys and little plastic animal figurines, and I would make up stories with those, too.
When outside or on the school playground or even waiting for the bus or on the long bus ride itself, I'd slip into the personas of my characters and pretend to be them, kind of like active daydreaming. This was also a coping technique to deal with unpleasant situations, for example, if I had to wait in the dark and snow for a long time, I'd "become" a tough soldier character, or if I was upset and crying, I'd "become" a character who was grieving a loss and was better emotionally equipped to deal with such things, so I'd stop crying sooner. Unfortunately, I made myself lose this ability since I thought it was unhealthy, yet I never managed to develop another coping mechanism to take its place. :sigh
I still passively daydream constantly about being my characters to this day, just without the emotional coping benefits. Most of my daydreaming centers around plots of my written and unwritten stories. (I used to write a lot but now I daydream about my stories more than I write them, largely because I have no readers and thus no motivation.) I have a lot in common with maladaptive daydreamers except they're trying to stop engaging in this activity because it interferes with their social lives, whereas I have no intention of stopping because I have no social life and my life is otherwise quite dull and lonely and empty. So it kind of sucks that I can't really identify with regular people OR with other people who do this, either.
Tl;dr, almost all of my childhood hobbies involved imagining I was somebody else. :/