If you’ve got some hard, stuck-on grossness inside your toilet that you simply can not scrub off, grab a pumice stone. I’ve had some disgusting crud under the rim of my toilet that couldn’t be Kaboomed/scrubbed/bleached, sweet-talked away.
I took my pumice stone (that I use for my feet), and with some elbow grease, got rid of it. It ate up over half the stone, but that’s just fine. Wet it a little bit (you’ve got water right there in the bowl) and scrub away. No chemicals, no fumes. Good stuff.
I have another post in queue regarding my thoughts on bathroom cleanliness, but I’ll save that for another day (here it is).