Hiya o/
was curious: can one add scripts into pihole or maybe somehow attach a script next to pihole on the same RPI?
i am being really vague, i guess... but i've randomly been snooping around on ways to remove ads from prime video on a bedroom Hisense tv... and found a little script that looks like might actually work. so, want to know if there is a generic way of slapping it onto pihole and test it?
You sure are being vague.
What do you mean by “custom script”?
Is it a custom list of domains to block?
Or is it a script that runs on the Hisense TV?
sorry for the vagueness, but if i knew more about it, i would not be asking this... my sincere apologies, bud 
i'll try my best, here:
pihole in general looks at the request and either lets it through or not - in noob's terms.
does pihole support any scripts that would let the request through, but filter coming back data in any way? basically, trying to turn pihole into something like AdBlock Plus, really. on my pc, i use brave and adblock plus. i see no ads on it, nowhere. but on my tv, when i start digging into amazon requests, either ads disappear for 5 minutes, but appear later on... or i break amazon app and it doesn't work on tv at all.
hisense is not that friendly when it comes to adding scripts or apps that are NOT on their personal app market (vidaa).
not seeing ads on amazon prime when using pc, means that ads can be removed. sooo... scripting it is.
curious if pihole has such functionality.
That would be pointless, as the only option for a filtering DNS forwarder really is to replace the DNS reply, and that decision does depend on the domain entirely, not on the DNS response's contents.
You should instead focus on why DNS requests seem to be blocked initially, but are allowed after some time.
This would usually indicate that Pi-hole is being by-passed.
Please upload a debug log and post just the token URL that is generated after the log is uploaded by running the following command from the Pi-hole host terminal:
sudo pihole -d
or if you run your Pi-hole as a Docker container:
docker exec -it <pihole-container-name-or-id> pihole -d
where you substitute <pihole-container-name-or-id> as required.