The Doom Patrol's Beast Boy meets the Teen Titans in a story by Haney, Bill Molno and Sal Trapani from issue 6 (Nov/Dec 66).
Doom Patrol members Robotman, Negative Man, Elasti-Girl and the Chief get small roles at the top of the story. At this time, Beast Boy was not yet a real member of that team, as his guardian, Galtry, refused his permission. Beast Boy hangs around the Doom Patrol headquarters, but just winds up pissing everyone off.
So Beast Boy heads to a television station, and broadcasts a message to the Teen Titans. Robin, Wonder Girl, Kid Flash and Aqualad come to meet him, and are impressed with his animalistic shape changing powers. But once again, it turns out he needs permission to join the team. We find out that Batman, Wonder Woman, Aquaman and Flash all had to sign permission slips for their sidekicks to join the Titans.
Feeling completely rejected, Beast Boy runs off and joins the circus. He becomes a star there, but is not aware that the ringmaster and his animal trainer are using him, hypnotizing him into adopting a white monkey form that can hypnotize the audience, allowing them to rob the patrons.
The Teen Titans wind up coming to investigate the robberies, and adopt masked identities, passing themselves off as an acrobatic troupe. Their true identities get exposed, and the ringamaster forces them into battle with a mind controlled Beast Boy.
This makes for the most impressive battle yet for the Teen Titans, and harder for them as they do not want to injure the shape changing boy. They manage to break him free of the spell, and together they take down the ringmaster and his men.
The story ends with Robin making a plea to the readers, to see if they want Beast Boy to join the Teen Titans. It must not have been a popular idea, as Beast Boy never returns during this run. But it did lay the groundwork for him to become a member of the team later on, and Beast Boy, who continued appearing in Doom Patrol, would next be seen with the Titans in the 70s, as a member of Titans West.