why do I get a boner sometimes when I think something is cute, like a little chibi bunny or something?

sometimes when I see cute little animal characters (especially with visible belly buttons fsr) I get a massive boner. I don't imagine myself fucking them, that would be nasty, I would just want to hug them and pet them, like what you should do with cute things. although I think women's bellybuttons are also hot, that feels different. is blood flowing to the phallus just a response to strong pleasure?