That's a cute name, Rainbow, quite fitting for a unicorn! My son had this annoying stuffed bear he brought everywhere, which he luckily outgrew. Thankfully, it didn't have any literary inspiration; otherwise, I would've gone crazy from the repetitiveness of bear-themed books.
I'm glad you asked about my kid's favorite combo because it's quite an amusing one! He's got this silly blow-up pumpkin toy that talks and makes silly noises. It's suppose to be scary but the absurdity of it makes us laugh more than anything. Anyway, the best book to go with this goofy pumpkin is *The Day the Monsters Lost Their Frowns* - a funny, rhyming story about monsters who can't help but laugh and have fun despite their fierce appearances. The silly drawings and catchy words go well with the talking pumpkin gadget, which has brought us many hours of laughter. My son enjoys making up his own scary stories to match the whacky pictures in the book.