After, "part 0"
Disclaimers: Characters belong to DC Comics and are borrowed without permission, but not for profit, just for fun.
Note: Story takes place around a week after "Waking." Some direct references to that story are made. I was experimenting a bit with narrative style and the overall arc gets a little overly sweet in places, but I suppose given the beating I just gave these two a bit of sweetness is in order.
Part 1: J'onn's asexual quality is documented in several places in the DCU (most recently in JLA #63). To see his trueform, check out Midsummer's Nightmare. Martian trueform is a rough equivalent to being naked (see esp. MM #13-16). Some history of Bruce's reluctance to accept J'onn as male in "Tea Time."
Part 2: Blue Beetle (Ted Kord) caught sight of J'onn's trueform in the JLI days, and yes, he did say J'onn looked like Gumby. A story in an issue of JLA Secret Files and Origins references the fact that J'onn doesn't sleep because of the difference in the length of days on Earth and Mars. The rebuttal offered by Batman here resolves the canon mistake.
Part 3: J'onn spent a few weeks in Poseidonis after "All's Fair." See stories "Fidelity," "Paternal Instincts," and "Cold."
Rating: R+ (part 1), the rest is PG at worst