Hm. Yeah, I guess just not really worrying over the reason is an option. Really it's all about what kind of story is being told. Just about a group of super heroes? Who cares about a reason! Want an over-arching villain? Well, having that massive universal collide would be a reason for all the heroes to fight someone all-powerful.

Well I guess I have some idea what I'm doing.

Maybe.

1. A newly created "police force" for both universes that has to deal with problems in both universes. Joker loose in New York City? Mandarin attacking Star City? We got this! Maybe there's a classic "new injustice league" is created to oppose and maximize chaos. Maybe they're trying to truly connect both universes, an event that would cause reality to just crumble as two universes should never fully coexist.

2. Galactus, with new sources of food, has set out in the DC Universe to consume new planets. He manages to consume Mogo, the Green Lantern Planet, and gains access to a limited supply of Will. With even more power, he sets out to consume so much more within both universes. Even gaining allies in cosmic villains from both universes.

3. Mongrul, now with access to more "willing" gladiators for his colesium on his planet, sets out to capture some of the best fighters in both universes to host the ultimate war game. Will our heroes be able to stop him in time? Or will they soon become part of the war games and have to fight to survive or plan the deadly escape?

4. The Brood have spread to both universes and is being led (mind controlled) by Starro to conquer all worlds! With a host of villains and super heroes, as well as the Brood, under his command...will our heroes be able to stop the starred conqueror?!

O.O Sooooo many great ideas! Maybe it'd be best if we all took a vote and then went from there, since some want a more simpler plot while others want one that is a bit more fleshed out..? Yay or nay?

<Snipped quote by Winter Blooms>

If we vote, I think it is more than one topic to vote over.
Who?
()Cannon Only(including cannon alternate)
()Amalgam
()Originals Only
()All
When?
{}Past
{}Present
{}Future
{}Alternate timeline
Where?
[]Two worlds permanently linked(an open portal in a major city for free flowing traffic 24/7, for example.)
[]Two worlds separated (rare occurrences and limited travel)
[]One world amalgamated (supergladiator flying over Metrocago while darkclaw swings through gothyork)
[]One world apart (Batman trades blows with doctor doom in the blue forest of Pandora)
Why?
<>Contest(good versus evil, one universe versus another)
<>Conflict(all versus one opponent)
<>Conquer(some seeking to use this opportunity to their advantage)
<>Confusion(WTF?!?)

As long as things are nice, simple, and I can use an original character, I'm down with anything.

If I must vote, then...
(All)
{Present/Future/Alternate Timeline}
[One World Amalgamated/Two Worlds Permanently Linked]
<Conflict/Confusion>

(X)Cannon Only(including cannon alternate)
()Amalgam
(X)Originals Only
()All

{X}Past
{X}Present
{X}Future
{X}Alternate timeline

[X]Two worlds permanently linked(an open portal in a major city for free flowing traffic 24/7, for example.)
[X]Two worlds separated (rare occurrences and limited travel)
[]One world amalgamated (supergladiator flying over Metrocago while darkclaw swings through gothyork)
[]One world apart (Batman trades blows with doctor doom in the blue forest of Pandora)

[]Contest(good versus evil, one universe versus another)
[X]Conflict(all versus one opponent)
[X]Conquer(some seeking to use this opportunity to their advantage)
[X]Confusion(WTF?!?)