In one play through i found a friendly dog by NCRCF then on another playthrough i found a dog treat. i was going to take it to the dog to see what happens but when i got there the dog wasnt there. has this happend to anyone else and what happens.

I found the friendly dog as well out side the NCRCF prison. Never found a dog treat though. I wish I could adopt him and name him after my old reliable pup from FO3...

Yes I met that dog outside NCRCF too.

Oddly, when I first went there, there was a friendly dog, and a friendly coyote just outside the front gate area, near the parking lot. I wondered what they were for.

I've seen a friendly Gecko before. He was just running in circles while making frantic huffing noises. I couldn't click on him or anything. I thought it was probably a glitch, but I've seen that dog, too, so..hm. Makes you wonder.

Maybe all of these friendly animals were once part of a quest that was not finished/implimented.............. like starting a wastland zoo!
lol, maybe if you look hard enough you'll find a friendly deathclaw!!!

You'd have to walk up close to one to find out. You'd have much better odds in the casinos.

I remember a friendly Deathclaw in FO3

I encountered a friendly brahmin on the strip.

what happens on the strip stays on the strip...