While the teamups of headliner heroes such as the Justice League in the silver age and, prior to that, the Justice Society in the golden age, were fairly common... minor mystery men generally kept within their corners of comicbook continuities. Partly this was due to their lack of notoriety, and popularity. However, on occasion, these did occur with startling results.
There was the time when the criminal League of Challenger-Haters stalked the vacationing objects of their vitriol. And without their gadgets, the Challengers of the Unknown may have been helpless versus their inhuman opponents, were it not for the Doom Patrol who leant a hand. Elasti-Girl vs Multi-Woman... Kra versus Robotman. And, of course, the more modest masked men Star-Spangled Kid and Stripesy crossed paths... not to mention almost running into each other.. with the Dynamic Duo in pursuit of the Joker. Good times.