In the season finale, there's a moment where five of the six Space Rangers stand on a rooftop and publicly announce that they're the Power Rangers in front of everyone in Angel Grove, the setting of the shows to that point. That includes Bulk and Skull, who had known four of the five Rangers for around a year and half... namely, since they replaced four of the Turbo Rangers. Considering Bulk and Skull knew every Ranger in their civilian identity to that point, they could easily figure out who the previous Rangers were. Then in the Power Rangers Wild Force episode "Forever Red", there's a scene where Bulk and Skull nervously approach someone they knew in high school (Tommy, to be exact), who just happened to be a Power Ranger. Whilst never stated, it looks like Bulk and Skull learned the identities of the Power Rangers after all.
Bulk sounded confused when he saw who the Rangers were, almost as if he were Expecting Someone Else. Remember, he and Skull started their investigation into the Rangers' identities years before with the original iteration of the team. It's likely that they had some suspects, even if they never figured out who the Rangers were. It's also likely that, since the attacks stayed focused on the same city the entire time and the Rangers only changed outfits twice before leaving for space (once from Original to Zeo, and then from Zeo to Turbo), he thought the Rangers had maintained a consistent lineup that entire time. He's probably trying to process that he and Skull were completely off the mark in their early theories and trying to piece together how a group of relative newcomers could have been saving Angel Grove years before any of them even lived there.
Speaking of the above scene, why would the rangers risk "losing the protection of the power" by committing one of Zordon's three cardinal sins? To the untrained eye, it might seem like it was a last resort to save the innocent civilians, but think about this for a moment: Obviously, the power rangers don't hide their identities from each other, right? What the rangers did was a sign of respect for Bulk, Skull, and the rest of the city after that whole I Am Spartacus stunt: That day,Everyone really was a Power Ranger!
Why did Andros have those morphers lying around the Megaship to give to the former Turbo Rangers? Because he used to have a team of more than him and Zhane, and they outright DIED in the fight against Dark Specter's forces. This explains so much of Andros' early behavior, why he doesn't want the other Rangers around (he doesn't want to watch anyone else die because they accepted the power) and why he held on to the idea that Zhane could be healed, because Zhane was his last connection to the old team. Not to mention why he's flying around on his own in a fully equipped spaceship.
The Rangers tell Astronema they liked her better as a blonde. Consider that Astronema is natural blonde usually good when she has blonde hair.
The Rangers stop hanging out at the Angel Grove Youth Centre's Juice Bar, with little explanation. There is one, however - they went to the Juice Bar so that if Justin ever had to say where he was, he had the very plausible explanation of the Youth Centre. Once Justin's no longer part of the team, the Rangers begin hanging out at the Surf Spot instead.
Blame Megaranger which the show is based on, they travel on surfboards!
If the bad guys had a missile that could take out Earth in one shot, why bother with the surface attack in "Countdown"? Did they want to lure the Rangers back to Earth before they blew up the planet?
They probably wanted to gather humans as slaves to serve them after their victory. Also, by taking the hostages, they would draw out the Rangers so they could be fought and defeated, rather than continue to sow resistence amongst the survivors.
Maybe it's more Fridge Squick, but the episode mentioned under No Ontological Inertia. If the spell the shapeshifter performed on Ashley hadn't worn off with its death, Andros would have ended up dating a girl who looked exactly like his sister. Then again, maybe it would have turned that subplot into an Aborted Arc, specifically to avoid that Squick.
Then again - morphing restored Astronema to her normal appearance, maybe it would have done the same to Ashley even without destroying the monster.
When Zordon's Energy Wave wiped out all the evil forces on Earth, what about the thousands of Velocifighters flying around the planet? If the wave only disintegrated their pilots, that would mean you have thousands of aircraft crashing all over the planet.
In every instance the wave destroyed someone it took all their gear with them. Even changing things to a more benevolent form when it simply purified them.