Can celestial be swapped for fiendish using Summon Monster speels?

[Kish]

Which reads to me like the RAW says "Yes, but..."
If the OP is a Good cleric, then he would not be able to swap the templates (because he could not summon Evil creatures...) If he is "good" (but Neutral) he could.


That seems to be specifically what the feat is for, so I don't see why it wouldn't work... (Of course, the [Exalted] tag is a pretty hard lock...)

Absolutely. Go nuts with good-aligned fiendish octopi.

RAW aside, there's no good reason not to be able to summon a Celestial octopus or a fiendish badger.