From the letters column in Challengers of the Unknown #86 (April-May 1978):
The editorial reply:
Well, I don’t know about you, but I’d totally be in favor of an “Adventures of Alec Holland” series. In fact, in a way it looks like we might be getting a little bit of that in next week’s final issue of that one series I don’t want to spoil by mentioning that Swamp Thing may or may not have made an appearance in the previous issue.
We’ve had the occasional Alec Holland adventure in the various Swamp Thing titles, usually when he reverts (or imagines he reverts) to human form, like in the last issue of his original series and the couple of Challengers of the Unknown issues which followed up on those plot threads.
And then there was this, Alec Holland’s one and (I think) only appearance in the DC Animated Universe comics, from Batman Adventures Vol. 2 #16 by Ty Templeton, Rick Burchett and Terry Beatty:
Alas, at no time was there an animated universe Swamp Thing to go with our animated universe Alec Holland, aside from some sneaky cameos in the Justice League cartoons.
As an aside…there sure were a lot of typos in that Challengers letters column. In the scans you can see “there” used in place of “their,” and “permanently” spelled “perminately.” Not shown: “November” spelled “Nobember.” By the way, I was going back through some of my older posts as I was writing this and quickly spotted several typos of my own, so I’m not taking the high road, here.
And if I may quibble a bit with the original letter writer’s point…Holland didn’t spend “his whole life looking like that.” Even in real world time, as opposed to however much time allegedly passed in the comics, Holland had only been Swamp Thing for about six years at that point. So let’s not exaggerate, Guy Who Wrote in to Challengers of the Unknown 30-Plus Years Ago!