It has generally come to be accepted by fans that all Green Rangers are air headed comic relief characters. However, out of the eleven Green Rangers to appear in the show, only Joel, Bridge, Xander, and Ziggy can really be said to have been air heads, and Tommy, Adam, Carlos, Damon, Trip, Cam, and Master Phant do not really count as the official comic relief characters of their teams.
Alternately, Green Rangers tend to be Memetic Badasses. Tommy, Adam, and Xander anyway.
Subverted with Tommy. While he wasn't a comic relief character, he could be established as one of the more forgetful members of the team.
Sacrifice the Zords! Explanation Refers to the senseless sacrifices of zords made by Tommy in Dino Thunder and TJ in Turbo (which came first but wasn't as well known a sacrifice)
Observe the viewing globe.Explanation In addition to being Zordon's catch phrase, it's also the name of a series of PWP fics involving the Rangers having sex with each other or dying while Zordon and later Billy watches. Amazingly, there's actually characterization and subtext to it
Banned in Australia!Explanation "Agony in Pink", an erotic fanfic about Kimberly being tortured to death, led to a Power Rangers newsgroup being banned in Australia
Geography doesn't work that way.Explanation Judging by the show, Angel Grove is a British colony in the LA metro area with an Indian reservation, home to plains Indians, nearby. It also has jungles, glaciers, and volcanos nearby, judging by the zord animation
Turbo is the worst season ever. No, Wild Force is the worst season ever.Explanation In Turbo, they replaced the entire cast with characters who quickly became The Scrappy, such as Justin, Dimitria, Blue Senturion, Alpha 6, TJ, and Ashley. There's actually a manifesto at Rangerboard about why Wild Force is the worst season ever
In later years, it's been supplanted by "Operation Overdrive is the worst season ever" for some people.
Too much pink energy is dangerous!Explanation In "Wild West Rangers", Kimberly questions why they can't recruit a Pink Ranger in the timeframe they were in. Zordon tells her that
The Power Rangers invented the Google Chrome logo!Explanation There is a logo in one of Ninja Storm's megazords that looks like the Google Chrome logo
Who's Madison?Explanation In Power Rangers Mystic Force, Blue Ranger Madison Rocca was so out of focus that people started saying Nick's bike got more screentime than her
The Red Ranger needs a manicureExplanation The Wild Force rangers are the only rangers to date with claws on their gloves
Why do people complain about Justin being 12? Operation Overdrive had a 2-year-old, and he was pretty cool!Explanation The Red Overdrive Ranger, Mack, was actually an android who was built 2 years before the series beginnings despite physically being a 17 or 18-year-old. (which raised further eyebrows on why his father built him like that...)
Will! Don't steal anything on your way out!Explanation A College Humor video called "Zordon is a Racist" parodied Will from Operation Overdrive in a scene. Will was not only black, but a Black Ranger and a professional thief, leading to Unfortunate Implications, which wasn't helped by his actor stealing a banner, either
Ronny has zordgasms and loves drills.
Conner is addicted to power-ups. Explanation Conner has the same Super Dino Mode power-up the whole team has, the same Battlizer every Red Ranger has, PLUS he has a "Triassic Ranger" transformation that requires him to steal energy from the other four rangers.
Power Rangers New Powers! They have powers, that are new! Explanation The fandom had quite a reaction to the poor explanation for the existence of the nameless five core Dairangers in Super Megaforce. This culminated in this parody trailer, popularizing the Fan Nickname "Power Rangers New Powers" for the Dairangers. The nickname itself was derived from the frequency of the words "new powers" during the first Dairanger scene.
"There's a simple explanation for that." Explanation (HA!) Said by Gosei when he's about to explain why Jake's Super Mega mode is green instead of black, only to get interrupted by an attack. This has since become the go-to line for any of Super Megaforce's plot holes (including the lazy inclusion of Super Sentai-only suits as noted above)
Yeeeeeeeeeeeaaaaaaaaaaaaahhhhhhhhhhhhh Explanation The catchphrase of the fandom's acceptable target, Jason David Frank.