Angst? What Angst?: Omega Ranger sure is chipper for a guy from a Bad Future that becomes stuck in another time and can't demorph without turning into a ball of light. And remember, Omega is an older version of Sam, the kid that considered B-Squad his first real friends. In his original timeline, B-Squad died, except for Z. - a fact that doesn't particularly concern Omega at all when interacting with them. And note that he behaved this way before he Set Right What Once Went Wrong.
After all, Omega is still an older version of Sam, and even if he can't still know if he succeded in his mission, he's still living both the dream of his lifetime, fighting with the legendary B-Squad and helping them on equal grounds, both going on in his mission.
Ass Pull: The show makes no attempt to explain the A Squad's Face–Heel Turn. As far as we can tell, they all just woke up one day and decided "Let's turn evil."
Broken Base: Some fans think its one of the best series, others despise it. Still others think that it's good, but not without flaws.
During the climactic fight in "Once A Ranger", each retro Ranger's theme song played during their segment of the fight (most had two shown). This is the theme that plays the longest, through Bridge and Mack's second sequence against Flurious all the way to the end of Adam's fight with Thrax.
Hell, in the aforementioned Operation Overdrive 15th Anniversary special, which featured 5 former Rangers returning, Bridge was included as the SPD representative, and as the Green Mystic Force & Blue Ninja Storm Rangers were used, they gave him an off-screen promotion to Red Ranger to justify his inclusion.
This may even be true in-universe: at the start of the series, Jack and Sky and Syd and Z have their respective personality clashes, but Bridge is the first to accept the newcomers while maintaining his relationship with the holdovers. And when the team presses Piggy for information on the alien who abducted Bridge in "Missing", Piggy says, "Oh, no. Not Bridge. He's the one of you I dislike the least."
Z and Syd are two of the most popular female Rangers, especially in the Disney seasons. The fact that their Sentai counterparts are Jasmine and Umeko helps.
Doggie Cruger. Whether if its because of the Furry Fandom, his Woobie backstory, or because he's the first mentor to go out into battle as a Ranger (not counting Tommy, since he's had a history of fighting beforehand).
Fan Nickname: The four unnamed A-Squad Rangers = Rachel (Pink), Cliff (Green), Ivan (Yellow) and Beevor (Blue) (the last being the most visibly alien one), To which Bruce Kalish approved at a convention so they are somewhat canon.
The Sentai version, Dekaranger, was known for its vehicles with names like Machine Husky and Machine Bull (as in bulldog), but these never made it into SPD except by accident. Enter the Jeep Wrangler, already a staple of the filmed-in-New Zealand seasons, now repainted in SPD colors, which led the fans to dub it Machine Dingo. Never mind that the dingo is native to Australia and not New Zealand...
The Battle Thong. Due to this seasons battlizer including (at least in its first mode) a, well...
Does no one even consider that Sam the Omega Ranger and Sam the kid that Z rescued are the same person? It possibly Doggie knows but just care.
Fridge Brilliance: It's already in canon from Power Rangers Turbo that morphing can change your body, seeing as Justin grew from child to adult. Changing Cruger's face is far less jarring a transformation than that. It probably is possible.
The planet Gallifrey showed up in a list of planets visited during In Space, so maybe the helmet has TARDIS technology?
In the first episode, Sky says that Bridge is not Red Ranger material. Cue the 15th Anniversary Special (See above). In that same episode, Kruger asks Sky if he'd follow Syd into battle if she was a Red Ranger, only for him to scoff that she's a girl. A dozen or so episodes later, and the A-Squad is revealed to be female... and a couple of years later...
Power Rangers beat Super Sentai in the first Female Red race.
The Scrappy: Sam. Specifically Future-Sam a.k.a The Omega Ranger, mainly because we don't know a damn thing about him. That he does appear in the finale, for all of three seconds, without his costume, was seen as an insult by the fanbase, and he rivals Cole and Justin for Most Hated Ranger Ever — those two win because they have personality quirks and flaws that make them unlikeable — Sam is hated because he lacks any of this, due to the writers bypassing him as often as possible. Bruce Kalish has acknowledged that Sam could have been handled better.
Inversion with most of the alien allies, as they look more like aliens rather than furries.
They Wasted a Perfectly Good Character: Both Sam and Morgana, we know next to nothing about these characters and they're mostly there to give their opposing sides an extra warrior. For Sam, it's due to Executive Meddling since Disney, a multi-million dollar entertainment corporation, was too cheap to hire an adult actor to play him. Despite the fact the show had already established a plot line for him earlier in the season and had the potential to explore it. For Morgana, its largely due to the story just forgetting about her. She started off interesting at first, using a book to make monsters and having to earn her childhood back mid-season when Grumm reverts her back into an adult. But beyond that, we never know why she hated being an adult, where she came from and why she works for Gruumm in the first place as the show focuses on other plotlines. Come the final battle, she's just defeated rather unceremoniously and that's the end of that. Pity.
They Wasted a Perfectly Good Plot: More like characters traits from Dekaranger. In the original series, the rangers had several specializations like Hoji being a sniper and their guns suggested those characteristics. Those were never used in SPD.
The A-Squad as villains. The idea of the rangers having to fight the team that were originally supposed to just be back-up for was a good concept, they get very little development so apart from they're backstory, they aren't all that different from the usual bunch of evil rangers.
During the All Your Base Are Belong to Us at the end, Broodwing could have released all of the villains that had been captured, but he didn't. It would have made things so much more difficult for the Rangers, too.
During the Body Swap episode with Sky and an alien criminal, Sky desperately tries to figure out a way to let the others know what happened and it never ONCE occurs to him to go to Bridge...the PSYCHIC! The climax ends with...the robotic dog figuring it out.
Tough Act to Follow: SPD can be seen as this for the other three Kalish Era Seasons, as it's generally seen as the only really good one (Mystic Force and Jungle Fury are seen as So OK It's Average, and Overdrive... well, that's a can of worms we aren't gonna open here).
What an Idiot: Broodwing, for thinking that trying to bring back the Dino Rangers from the past to help him destroy Earth was a good plan. Wereas in previous team-up episodes where that kind of thing happened, the involved villains (Trakeena and Lothor) were careful to ensure they could control those they brought back through Mind Control or other system, he just brings them back and expects them to agree with a We Can Rule Together speech. That despite the fact that, like all Rangers, they had been protecting Earth for years... yeah,very smart Broodwing.
The Woobie: Even after R.I.C. proves how completely Bad Ass he is, the other characters still have a hard time taking him seriously and use him as, among other things, a refrigerator.