1) An expression that means just what it says; 2) a Griivarr Worlds Holoshow about two clones who fall in love; 3) the theme song from the aforementioned Griivarr Worlds Holoshow, arguably the most irritating theme song ever written. (Lyrics follow.)
Double Trouble, Double Dynamite,
More trouble when they’re friendly,
Than when they fight.
Birds of a feather, they stick together.
Trust me when I tell you,
They’re more than tight.
One’s retiring, the other bold.
One’s inspiring, the other cold.
How it happened, we just can’t say.
Two crazy clones like night and day!
Double Trouble, Double the fun.
Two look-a-like lovers are better than one.
Take Trouble and Double the critical mass,
Get ten to the tenth the kick in the ass.