Five years before that, during a Halloween special, he had been stabbed in the heart by a demon's spear. A demon spear that was referred to as a 'squid-on-a-stick', no less...
Megatokyo has this fairly early strip depicting what would happen if Fred worked without Rodney, or vice-versa. Two years later, Rodney stopped contributing to the comic; the old joke strip turned out to be, in many ways, pretty accurate.
1/0 declared "war" on another webcomic on September 11th of 2000.
An early running gag has Roger vehemently deny being a werecoyote, despite the fact that nobody accused him of being one. By the time he reveals that he is one, the strip's taken a dark enough turn that a terrible bloodlust, to which his mother has already succumbed, is a major plot point.
Another early story has April and Roger get possessed by ghosts inhabiting a television set and a hairdryer, respectively, to do battle. Later stories show that Roger is particularly vulnerable to possession by Satan in his werecoyote form, and April's gradual progression to Yandere and eventually Manipulative Bastard is implied to be at least partially due to Satanic influence.
The king of them all, however, is in the earliest storyline of note: A paranoid Marsha stabs Mike, hospitalizing him. Immediately afterward, she blames April, because "Miss Wimpy didn't want any bloodstains on her wimpy clothes!" It's Only a Flesh Wound, and Mike (a consummate Manipulative Bastard) recovers perfectly, then leverages Marsha's guilt to start off their relationship. In a much later storyline, Mike is Killed Off for Real when April, following an argument with Marsha about her relationship with Mike, fatally stabs him.
The Order of the Stick manages to create an Aneurysm Moment retroactively with the punch line of this strip. The aneurysm doesn't come until you remember (or read, if you hadn't already) the Start of Darkness prequel in which you realize just how low Xykon can go (and how painfully aware Redcloak is of it).
There's also the Cliffport police chief talking about how the mayor was going to have his head on a pike because of the ruckus Nale caused. A couple of strips later, Nale cuts off the Chief's head and impales it on his sword.Mmm...shishkabobs.
"It may be the last night alive for many of those girls you just told to 'chill out'. It might even be the last night for you, or one of your friends."
Then there's this strip, in which The Reveal is that Shojo's advisor is the ghost of Roy's father, who remarks, "You were maybe expecting Patrick Swayze?" Of course, now that Patrick Swayze is actually dead...
Elan picturing Roy as a surrogate older brother becomes less funny when you realize that Roy really did have a younger brother who might have become a bard, had he not died in an accident at a young age.
In one strip, Xykon says this to Redcloak after he murdered Tsukiko.
Xykon: If you had to smoke her, you had to smoke her. Hell knows I've had occasion to off an uppity minion in my day.
This sounds like Xykon being his usual Affably Evil self, until you've read Start of Darkness, where Redcloak's younger brother attempted to kill Xykon to avenge his family, and Redcloak was forced to kill him. Its one of many ways Xykon subtly torments Redcloak.
In this strip, Haley claims it'll take "200-foot tall flaming letters" to help convince Elan that his Affably Evil long-lost father is really bad news. This strip makes a rather dark joke about it when that turns out to be the case, as Elan his horrified when his father spells out Elan's name in the burned-alive bodies of rebellious slaves, the same ones Haley and Vaarsuvius freed in an earlier strip.
A rare case of averting this trope: In the print edition of the first run of comics, there's a previously-omitted comic during the battle with Xykon in which Vaarsuvius, paralyzed by a ghasts' touch, sits helplessly while a trio of demon roaches sits on his/her head and crack wise. Why was it omitted from the online comic? Because the morning that it was scheduled to be posted, Christopher Reeve died. The author (wisely) pulled it, only letting it see the light of day as a "bonus strip" over a year later.
Especially good because the strip more-or-less illustrated whyDuke Nukem Forever didn't come out when it was supposed to, long before anyone outside the production company knew. The company just kept playing around instead of delivering the promised game to a distributor (the distributor changed midway); by the time they took the deadline seriously (Take-Two was less patient than the previous distributor), they were no longer able to get the money to complete it.
Oh, yeah, and... a few pages later, the upper-right poster would also apply.
And now, it seems that the upper-left poster also applies. Jeez, will Rojo take the BLU demoman's spleen next?
ThisAchewood strip suddenly got a lot less amusing when news of a sex tape (link SFW), falsely attributed to be of the real Meg White, was released almost a year afterward.
In Gunnerkrigg Court, Kat's belongings sometimes have the names of bands printed on them. In this page, her shirt reads Sparklehorse. Mark Linkous, who led that band, committed suicide 2 months prior to the page being published. Considering the 30-page buffer kept by the author, it would seem that the page itself was made a few weeks before it happened.
It has been confirmed by Word of God that this was intended as a tribute.
This strip of A Softer World illustrates what seems like a rather improbable idea of what causes terrorists to be terrorists. But a later sociological study discovered that many of them don't really care about their cause, and if their mission is actually accomplished they just move on to another extremist group. It concluded that a large proportion really aresocial rejects who can't find friends anywhere else, and are willing to kill for the sake of that bond.
In Yu+Me: Dream, in Part One, Jake sarcastically tells Lia, “I’m just pretending to be gay for all of the social benefits it brings,” the joke being that so far in the comic, he’s caught nothing but flak for his homosexuality. In Part Two, after we’ve found out that that everything in Part One was essentially a reality show, it’s revealed that the actor who played Jake is actually a “straight douche” who won an Emmy Award for his portrayal of Jake. The commentary on this page suggests that he primarily won the award because of the (mis)perception that it’s a huge challenge for a straight actor to play a gay character.
In Misfile, after having a year of her life erased (the year during which she gained admission to Harvard, no less), Emily is told to "Enjoy all the extra time you've got." It took on a whole new meaning once you realize that without the misfile, Emily would've died in the same car accident that sent Molly to the hospital.
Shortpacked! had this strip. The panel with Amber saying she's pregnant suddenly becomes really disturbing due to Faz being Amber's (half) brother.
Roommates has/had a Running Gag about Jareth failing to do good despite his best intentions and efforts... after the Dark!Jareth arc that got some pretty heavy subtext. As a fictional character he can't defy the story and his role in it, doesn't matter how desperately he may try.