Introducing Teddy by Jessica Walton
Plot Summary: Errol and his teddy, Thomas, are best friends who do everything together. Whether it's riding a bike, playing in the tree house, having a tea party, or all of the above, every day holds something fun to do. One sunny day, Errol finds that Thomas is sad, even when they are playing in their favorite ways. Errol can't figure out why, until Thomas finally tells Errol what the teddy has been afraid to say: "In my heart, I've always known that I'm a girl teddy, not a boy teddy. I wish my name was Tilly, not Thomas." And Errol says, "I don't care if you're a girl teddy or a boy teddy! What matters is that you are my friend."
Youtube link: https://www.youtube.com/watch?v=ddRmNpLYgCM
Errol and Thomas ride their bike, garden, eat lunch in their tree house, and play at the park. When Thomas transitions to Tilly (with no hesitation or rejection from Errol or his friend Ava), they do all those things again, really emphasizing that it didn’t matter what gender Tilly was. Again, the instantaneous acceptance makes this a good book to have in company with other books with trans characters to balance out the overall message.