JSA. Per Degaton was strolling through time, getting off on watching his enemies at their darkest moments, and he shows up at Fate's tower to watch Hector and Lyta Hall, recently resurrected, dealing with their new lives. He considers messing with them, but a voice from nowhere warns him not to interfere with "my parents", that they deserve their "happy ending". Per Degaton immediately relents and heads elsewhere.
The only person I can think of who would consider Hector and Lyta Hall his parents is Daniel, aka Dream of the Endless. As far as I know, the moment is never returned to or clarified, but Per Degaton backs down so readily that it could only have been someone of immense power, and Dream would fit that bill. The word balloon isn't Daniel's typical wobbly one, but that may just have been a printing oversight. In any case, I'm calling it an appearance of Dream, since I'm always on the lookout for any appearances of the characters from Sandman.