The Silencer is the only powerup that doesn't make any activation or wear-off sound and even the GUI lacks the icon for it. How fitting...
In the Mission Pack Sequels, the Enforcer shoots first and reloads later. While on a meta-level this could be considered a bug, it does make sense In-Universe, considering how easily they were dispatched, that they would be willing to learn from their mistakes to extend their survivability and dangerousness. Stops being the case in the 2023 remaster, where the Enforcer became streamlined in all products, even if it gained new attack patterns.
The overall increase of difficulty in Ground Zero. The Strogg already had to suffer the destruction of the Makron (thrice!), their interplanetary defence systems, their production lines and their moon. So now their Elite Mooks and top tier mooks had to receive upgradesnote the Medic now being able to recall units as the Medic Commander, the Tank Commander now shooting surprise rockets, the top Icaruses being upgraded with a Power Screen as the Daedalus, all the units now being able to jump over obstacles, the bosses being mook makers, etc..., while their last lines of defence were improved to the point they can absorb and deal much more damage than before. In other words, they're now privileging quality over quantity. This even goes in line with Quake IV and the many times Kane is accompanied by fellow marines and vehicle usage. Still is the case in the 2023 remastered edition, even if the Turrets were nerfed.
It's also easy to assume that the reason their The Reckoning upgraded and exclusive units aren't anywhere to be found in Ground Zero is because, well, they've proven to be quite ineffective: the upgraded Gladiator going back to the more precise Railgun rather than the slow but damaging Phalanx; the Ripper, Hyperblaster and Laser Guards not being damaging enough; the homing Iron Maiden being more prone to damaging herself than the enemies, and the upgraded Brains and the Gekk being just useless and ineffective overall. This is also why there are no Brains and Iron Maiden had to wait until being upgraded with teleportation and screaming attacks in addition to their rockets. In the 2023 edition, Beta Class Brains replace all old instances of the regular Brains.
An interesting thing to note is the mission order: after establishing the communication to your base (thus turning the whole Base Unit area into an actual forward base), the first mission you're given (in the PC version) is to disable the Strogg logistical train and Stroyent processing plantnote Ok, the name wasn't given in this game, but a posterior, canonical game did, the latter of which requires you to disable the security grid and navigate through the mines. Then you move out to taking down actual objectives. By the time you reach the capitol of Stroggos, you're well armed and the Strogg forces are easier to take down. In other words, "amateurs talk about strategy and tactics, but professionals study logistics".
It's also easy to assume, if The Reckoning and Ground Zerodo take place after the main game, that the reason why you aren't given any logistics-related mission and go straight to the "heavy" objectives is because there's no logistics chain to destroy, everything was already done in the main game.
As for the PlayStation version, it cuts the logistics-related objectives and goes straight to the "heavy" objectives. If we assume that Stepchild is the protagonist of this version (judging by the use of the Ground Zero intro and ending cinematics), it's clear and makes a lot of sense why: Bitterman is already taking care of the Strogg logistics, Stepchild only has to complete objectives related to the area he's just dropped.
Finally, Viper's mission chains are separated from the rest. At best, he's visiting places with similar areas to the rest of the team.
The Makron is taken down multiple times: the main game, The Reckoning, the Playstation version, and all the instances in Call of the Machine. The manual mentions that the destruction of the Makron may send the Strogg into disarray, with every commander fighting for the right to lead the Strogg. Two possibilities may happen here, both of which are quite chilling:
Either the Makron noticed that there was a chance that Stroggos may be taken down for good and created copies of itself. Or...
All the Makron fought at the end of each game are said Strogg commanders being assigned different areas of Stroggos and the real Makron is The Unfought (until IV at least).
