Doom Patrol x Sandman Crossover

Neil Gaima's Sandman series had almost no interactions with the non-Gaiman-written DC Universe as it was being initially published (despite involving a great number of previously created DC characters like Destiny, Cain, Abel, & Lucien).

A rare exception is Doom Patrol #25, which came out the same month as Sandman #8. In it, Dream's struggles with Dr. Destiny are referred to:

It turns out they have a materioptikon in working order (despite the fact that Dr. Destiny's Ruby had already been destroyed; go figure).