As he digests Godzilla, Anguirus finds that some parts digest better than others. Fortunately some - but not all - of the spikey bits come back up rather than leaving the more painful way. Kong hangs around for this because it's a great, albeit temporary, source of new axe blades.
I drew this at a con a while back but I hated the anatomy so I never finished coloring it. I'd already put some time into it though, and some are likely to enjoy it, so here it is.