Clark didn't come back right. In fact, if you asked most of the Justice League, Clark didn't come back at all. However, one night, as Bruce is hacking Kryptonian technology into the Watchtower's computers, he discovers an errant strand of programming. It should be nothing. But it's nothing he's ever seen before; and finds his suspicions confirms when it begins communicating with him; then constructs itself a voice. Imagine Bruce's surprise when it's Clark's voice that comes across the Watchtower comms. Basically, this prompt is an excuse to have a story with a disembodied Clark who grows closer to Bruce, and has to connect to Bruce only through his voice.

SUPER BONUS POINTS and my undying thanks if this would lead to a scene where Clark directs Bruce to masturbate, and then talks him through it.

(Also, if you want to go the "Clark eventually finds himself a Kryptonian hologram body" route, I will be SO HAPPY.)