* AngstWhatAngst: Third Season. ''Last Kiss of Summer'' has Joe broken up and going on a revenge rampage to avenge the love of his life, who was killed in a car wreck as he was driving; she dies in his arms. Two episodes later, Joe's making out and flirting with other women as if nothing's happened, and the fiance' is never mentioned again.
* BigLippedAlligatorMoment: [[Series/CharliesAngels Jaclyn Smith]] makes a small appearance in ''The Mystery of the Hollywood Phantom'' as herself playing her character on Charlie's Angels. She ends up kissing Frank as he walks around a corner, an incident not mentioned again, and with zero effect on the plot.
* CompleteMonster: "Dangerous Waters": Vito Farina, aka "Mr. Hubbard," is a vicious [[RuthlessModernPirates modern-day pirate]] who targets yachts on the Caribbean. A crooked longshoreman before he faked his death to go into piracy, Vito always has one terrifying routine for the passengers of the ships he docks; he murders the men and dumps them overboard, and he spares the women to [[HumanTrafficking sell as white slaves overseas in China]]. Over half-a-dozen yachts have vanished by the time the Hardys find out, and [[CardCarryingVillain Vito is totally indulgent in how evil he is]].
* GatewaySeries: To not only the novels of the Creator/StratemeyerSyndicate, but also novel reading itself.
* HarsherInHindsight: The 2nd season (1978) episode ''Arson & Old Lace'', where an arsonist torches a skyscraper, not only trapping Joe Hardy and a small child in an office room, but also trapping Frank Hardy and Nancy Drew in the penthouse, with an un-working elevator & access to the roof blocked. After helping panicked people find the stairs through heavy smoke and flames, Joe delays his escape to follow a cry for help & finds a trapped child. He shields a child from an explosion with his own body [[note]]The explosion blows out a window and a good part of the outer wall; the shot of this, taken from outside & ground level, looks disturbingly like something crashing through the building[[/note]], then convinces the child to jump with him out of the window, as the fire has cut off all escape routes. Post-9/11, this episode is now hard to watch: people on the upper floors of the WTC were not only trapped by the raging fires below them, but access to the roof was also blocked. Many of those jumped to their deaths to escape the fire -- this makes the child's wide-eyed trust in Joe's assertion that they'd be OK heart-wrenching in hindsight. On top of that, WTC security guards stayed behind, helping trapped people find their way to the exit stairs -- guards who lost their lives due to their heroic delay of their own escape. The episode had only been meant as a cheesy ripoff to ''Film/TheToweringInferno'', but still...
* SugarWiki/HeReallyCanAct: Creator/ShaunCassidy & Parker Stevenson, two good-looking, easy-going actors with one-dimensional characters who mostly quip back and forth in a show that's only bait for teenage girls, right? Then we get Third Season. Hoooo, brother, do we get Third Season. ''Last Kiss of Summer'' has Shaun sinking his acting teeth into the dark side of Joe Hardy with a vengeance, portraying a revenge-obsessed, bereaved man who tramples over everything & everyone to bring his fiance's killers to justice. On top of that, throughout Third Season, Parker gives us a doubting & conflicted Frank Hardy, who is constantly put into roles of gaining someone's trust & then breaking it (usually in a way that traumatizes the victim); ''Game Plan'' brings this to a head, as the show implies that Frank [[spoiler: might have betrayed his brother and the federal sting operation in order to run away with the BigBad, a woman he's show to truly love, if she had just told him the full truth about her escape plans]].
* NightmareFuel: [[NightmareFuel/TheHardyBoysNancyDrewMysteries See here.]]
* RetroactiveRecognition:
** "The Mystery of the Solid Gold Kicker" has Creator/MarkHarmon as a football player and Terry Kiser and Martin Kove as blackmailers.
** "Voodoo Doll" guest stars Creator/KimCattrall.