I enjoy both eggplant and octopus, and agree that:

(a) they seem like they're going to be texturally similar
(b) yet they aren't at all.

I'm 35 years old and this shouldn't continue to surprise me. I also should be better at cooking eggplant by now. Mine typically comes out rubbery, although not octopus rubbery. (I suspect the cooking isn't the problem; I suspect I'm bad at knowing which eggplants to pick at the grocery, which is the same thing that stops me buying pineapple.)