In every installment of “If I Pass This Way Again,” we look at comic book plot points that were rarely (sometimes NEVER!) mentioned again after they were first introduced.

Today, we look at the one weapon that even Doctor Doom cannot protect himself again, so of course, it has never been used besides this one instance!

As soon as Doctor Doom received his own ongoing feature in Astonishing Tales (by Roy Thomas and Wallace Wood), the whole feature essentially became "The world against Doctor Doom." In each of the first four issues, Doom's castle in Latveria was being invaded by SOMEone.

In the first issue, Prince Rodolfo, who Doom deposed, seemingly invades before Doom takes him out, but Doom's latest creation, the Doomsman, escaped...

That Rodolfo turns out to be a robot. In the next issue, Rodolfo and the Faceless Man attack again, only this time, the Doomsman is on their side!

In the next issue (by this point, Larry Lieber was scripting the book. I would imagine over Wood plots, but I don't know for sure), Doom has to escape from his castle, but he then reveals that will destroy his own castle than to let his enemies have it...

Okay, so in #4, he then has his subjects quickly rebuild the castle. He heads to the French Riviera while they're constructing the castle, but while he is gone, Red Skull and Skull's minions (known as The Exiles) invade and take over the newly reconstructed castle!

So when Doom returns in #5 (now by Larry Lieber, George Tuska and Mike Esposito), he is attacked by his own castle defenses...

Including the ONE WEAPON that even Doom cannot defeat...Chemi-Sleep Gas!

Yes, folks, the only thing Doom cannot stop is...Chemi-Sleep Gas.

Doom later frees himself...

And renews his attack on the Red Skulled usurper (Skull, of course, does not use Chemi-Sleep Gas again for whatever reason) and Doom succeeds in getting rid of the Skull and his men through another form of gas. This time, it was Hypno-Gas for the win!

And Chemi-Sleep Gas, Doom's only weakness, has never been used again. That's pretty hilarious.

If you have a suggestion for a future edition of I Pass This Way Again, be sure to drop me a line at brianc@cbr.com!