You dont want to just do a cameo.
Its not a gimmick.
Johns teased Dr. Manhattans arc by contrasting his appearance inRebirthwith the return of Wally West.

Credit: DC
For Johns, West symbolizes the return of heart and hope to the DC Universe.
Doomsday Clockwill be drawn by Gary Frank and will kick off with a first issue releasing Thanksgiving week.
(Rorschachs sign actually said THE END IS NIGH, so things have trended downwards.)
Heisthe story, Johns explained, with no follow-up.
Well, some follow-up.
And Johns also mentioned a scene fromDoomsday Clockhe was especially proud of.
The smartest man from this world, DC, is Lex Luthor.
Thats all Ill say.
Its an easy guess that the smartest man fromanotherworld is Ozymandias, a.k.a.
Adrian Veidt, described inWatchmenas the worlds smartest man.
Left up to the imagination: whether Veidt and Luthor are working together or against each other.
Doomsday Clockdebuts Thanksgiving week.