Sometimes of other properties: the Moai Battleship is most likely a parody of R-Type's infamous huge spaceship from the 3rd level.
One stage in Jikkyō Oshaberi Parodius is a blatant pastiche of the Konami shoot-em-up Xexex.
Art Shift: In Jikkyō Oshaberi Parodius, the stages themed after Xexex and Lethal Enforcers use this.
Attack Drone: Well, many of the characters here have options. Although in the last game, you can play as Option itself.
Attack of the 50-Foot Whatever:In Jikkyō Oshaberi Parodius, giant versions of Hikaru and Akane become the level 2 boss. Also, Rika Chichibinita, the giant Vegas dancer, in almost every game save the MSX Parodius and Sexy Parodius.
Back from the Dead: Even though you clearly see him dead in a previous game, The penguin captain comes back in Sexy Parodius as part of a boss rush.
Boss Warning Siren: At one point in Fantastic Journey, the player encounters the Moai Battleship, with its placement randomly determined inbetween two of the regular stages. When the player is about to encounter it after clearing one of the stages, its own music theme plays instead of the chosen player character's theme and the message WARNING flashes on the screen.
Continuity Nod: the second level of Gokujō Parodius (a.k.a. Fantastic Journey) has you going underwater at one point. There you will find the corpses of the Pirate Penguin, his crew, and the remains of the Cat Battleship MK I, who were the first boss and miniboss in Non-Sense Fantasy, respectively.
Cool Old Guy: According to Non-Sense Fantasy,Vic Viper is 58 years old, and his upgrades are pretty average compared with the other characters, but he is also the only character that appears from the first Parodius to Sexy Parodius.
Cool Shades: The front face of the Moai Battleship likes wearing them.
Fantastic Journey. After several stages of wackyness, you have finally defeated the Octo-Queen. You find the treasure you've been looking for...only to find that there is a sentient classic cartoon bomb that has taken the place of the treasure. It's fuse has already burned to its last moments, and as a result, the dance club base is utterly destroyed by the ensuing explosion. During the credits, enjoy watching your character float amongst the shattered remains of the club you just raided. However, that doesn't stop you from entering theSpecial Stage.
Eagleland (Flavor 1): Eagle Sabu, a bald eagle dressed as Uncle Sam, serves as a boss in Non-Sense Fantasy.
Exported Weaponry: The angelic pig Michael (and even moreso Mike in Jikkyō Oshaberi Parodius) has the attacks of Darius's Silver Hawk, and Hikaru uses weapons from the Thunder Cross ship. And Ran is the R9 Leo. Mambo has Screw Laser from MSX's Nemesis-series and Search Laser from Xexex.
Kid Dracula uses the attacks of the ship from Axelay, another Konami shooter.
Also, Tako/Octopus has the Salamander configuration, while Pentarou has the Gradius III configuration... heck, almost everybody is probably this in some way or another.
Face-Heel Turn: Takosuke in Sexy Parodius does one of these just before the last level in an attempt to escape with all the money you earned in-game. He doesn't get far.
Home Version Soundtrack Replacement: The song that was used originally in the first stage of Jikkyō Oshaberi Parodius, "That's the Way I Like It," was changed in the PSP version (to the song Brilliant2U by Naoki Maeda), presumably by avoiding copyright issues, since it's an American song.
This happened to other tracks in the collection as well. Prior to it, the PlayStation and Sega Saturn release of Sexy Parodius replaced a arrangement of "El Bimbo" with "Symphony No. 40".
Our Giants Are Bigger: A recurring boss in the series is Chichibinta Rika, a giant woman in a Vegas showgirl uniform which parodies the Shadow Dancer.
Pandaing To The Audience: As seen in the page picture, a dancing panda is the first boss of Fantastic Journey. And its fight BGM is March of the Toreadors from Carmen.Hilarity Ensues, especially when you shoot it and its eyes pop out of its head like Blanka.
Panty Shot: You get one from Anna Baburowa,the first boss in Fantastic Journey (pictured above).You also get another one from her sister Zyiude in the sequel, Jikkyō Oshaberi Parodius.
Most of the background music is based on classical and folk music.
Everything else are remixes of Gradius music, such as the Big Core Mk III boss theme and the Aircraft Carrier (boss rush) music.
And some are from other Konami properties, like the Castlevania theme remix and such. Holy fuck they just used Brilliant2u in the first stage of Jikkyō Oshaberi Parodius (originally That's the Way I Like It) in the PSP collection!
Recurring Boss: If a boss has appeared in the series, chances are that it will show up again in another game. Mind you, not all bosses return ever game. Some are forgotten and not seen again until Konami wakes the hell up and goes back to see what else they made. The Cat Battleship has seen the most appearances, having appeared from Non-Sense Fantasy all the way to Jikkyō Oshaberi Parodius!, and that's not even getting into some of the other bosses.
Refuge in Audacity: Neutered cats? Bunny girls flying on torpedoes? Using a condom as a shield (for the stick figures on airplanes)? And that's even before getting into the contents of Sexy Parodius.
The most blatant example of the trope may be the flashing Moai's from Jikkyō Oshaberi Parodius, complete with pixelated genitalia...
Spiritual Successor: Otomedius seems to be this, what with two of the Parodius bosses appearing in Otomedius Gorgeous (Eliza the Mermaid and Yoshiko, Empress of Easter Island respectively). Parodius seems to live on through pachinko and pachislot games, however.
Taking You with Me: Decoration Core MK II, or also known as Lips (Stage 5 boss) in Jikkyō Oshaberi Parodius tries to do this after defeating it. If you know this is coming, you won't have trouble avoiding it. Of course, one must be careful of suicide bullets too...
Talking Poo: You can see a living poo come out of a toilet if you destroy an specific Moai head in the second stage of Jikkyou Oshaberi Parodius. It's dressed in a way reminiscent of a certain magical girl show.
Updated Re-release: A compilation of most of the games (except the Spin-OffParo Wars) was released for the PSP in 2006. It contained a remake of the MSX original, the PSX version of Jikkyō Oshaberi, and the arcade versions of rest. Due to copyrights involving some of the songs, Konami replaced a few of the tracks with replacement music.
Weapons-Grade Vocabulary: There's a weapon that the attack is nonsense phrases such as "SHAVING IS BORING" coming out of your spaceship.
The mermaid boss in the second stage of Fantastic Journey attacks with laughter.
We Help the Helpless: The plot in Sexy Parodius revolves around Takosuke opening an agency to help people in whatever problem they have. In the end, however, Takosuke isn't exactly intent on staying faithful to that.
Widget Series: It's not a surprise that Western audiences are weirded out by this series.
Zero-Effort Boss: The final boss in most games is this. This is given since this is a parody of Gradius, after all.