Alternate Character Interpretation: Did Crypto ever really care about Natalya, or was his fondness for her purely sexual? Some of their interactions suggest the former, while the ending and casually brushing her death off in the next game suggests the latter.
Anticlimax Boss: An irritating number of examples, though some are more because you can become rather overpowered over the course of the game (Meteor Gun, anyone?)
Oranchov's Blisk mutant form might give you some trouble, since it comes early in the game. Unless you use the Anal Probe (which you find mere moments before the fight) to turn him human again. He's about as squishy as any KGB Agent.
Silhouette and possibly General Armquist, though Armquist was definitely more of a challenge. Played horribly straight in DAH!3, in which some of the bosses barely even move, and especially if you have an upgraded Ion Detonator, except for Henri Crousteau.
Best Boss Ever: In contrast to the above, we have the well remembered fight with Kojira.
Ensemble Darkhorse: It's arguable that Pox is more popular than Crypto, especially after Crypto goes native. Though considering who voices him, it's not hard to believe. Silhouette also counts.
Evil Is Sexy: Silhouette, the main antagonist of the first game. DAMN that suit was tight!
Goddamned Bats: Missile launchers in the first and second game. In the first game, they launch a single missile that is near impossible to dodge and does a crap ton of damage to your saucer. The damage is toned down in the second game, and the tracking less potent, but now they launch THREE missiles at once. Add to the fact that on high alert levels, they show up everywhere and can now move, and you will be swooping, ducking, weaving and dodging to avoid the buggers, as they will fill the sky VERY Quickly. And to top it all off, there is a graphical bug on the PS2 version of the second game, which removes the exhaust contrail on occasion, meaning you won't see the rockets until it's too late.
It's Easy, so It Sucks: Destroy All Humans! 2 and 3 are on the easy side. Critics didn't enjoy it. (the third in particular)
It's Short, so It Sucks: All of the games are relatively short. The first two would have been even better if they were longer.
It's Popular, Now It Sucks: The series has gained a cult following, as well as fan haters, trolls, and the like. Doesn't help that the series took a dip in quality once developers tried to branch the franchise out with two games at once.
Nightmare Fuel: Crypto himself; a nigh unstoppable killing machine who plans to rip out your brain and destroy your entire town. Not to mention, he's President of the United States. If not for the game's over the top tone, he'd be fucking terrifying.
Replacement Scrappy: The Nexos from Path of the Furon to the Blisk. They look similar and even have a similar reveal (complete with Oh Crap! moment from Pox), but don't nearly leave the same impact.
Romantic Plot Tumor: Natalya and Crypto. Natalya even gets some status as The Scrappy, despite the fact that Crypto is the one hitting on her. As mentioned elsewhere under Pretend Prejudice, by the time DAH!2 rolls around, Crypto's only concern is having sex with anything female. This is worsened by Natalya, as Crypto falls madly in love with her. And so, as a result, Crypto spends the entirety of DAH!2 trying to have sex with Natalya, not even caring about what his enemies are up to.
Surprisingly Improved Sequel: While the story and characters can be debated, DAH2 expanded and improved on the first games features, and brought just enough new stuff to the table.
That One Boss: Crusteau in Path of the Furon. He can empty Crypto's maximally-upgraded health bar in exactly two hits, and whittling down his health bar with the few weapons you have that can hurt him takes forever.
They Changed It, Now It Sucks: Many people claim that the changes in Big Willy Unleashed and Path of the Furon made them suck, and that they weren't neary as good as the first two. This is also mostly blamed on the two developers who picked up the series after Pandemic was bought out by EA.