There is a great Cardy cover on Teen Titans 33 (May/June 1971), although it really doesn't tie in to the Skeates, Tuska and Cardy story very well.
Picking up from the previous issue, Jupiterius allows Mal Duncan and Kid Flash to see through the door they opened, and they come across the skeletal form of the cave boy they killed. There are cameos once again of the versions of Superman, Batman, Flash and Green Arrow that inhabit this alternate reality, but they really don't do anything. By standing up to the skeletal cave boy, which is really just an illusion, the two heroes pass Jupiterius' test, and he gives them a mystic water to drink, which takes them back in time to just before the death of the cave boy.
Given a second chance, Mal and Kid Flash manage to make sure the cave boy does not die, but then wind up bringing him back to the present with them. One would think that would mess up the time stream, and reality, just as badly, but it doesn't.
The cave boy gets named Gnarrk, because he keeps saying that. Mr. Jupiter gives the Teen Titans the assignment to civilize him and make him a member of society. Robin has some time off of university, so he comes to join Mal, Kid Flash, Wonder Girl and Speedy in doing this, but really it's Lilith who is the one that can telepathically communicate with Gnarrk, and helps teach him to speak.
Wandering the city on his own, Gnarrk happens to be on the scene to see that a prominent city councilman is really tied to the mob, and then has to testify to this in court. Lilith goes into overdrive to get Gnarrk prepared for this, and the Titans help stop hoods from killing him before he can make it to court.
It's an ok story, but the courtroom drama stuff doesn't seem to fit. Gnarrk returns the following year.