Chapter One: A dull New York

Donnie makes a machine that uses Mikey's mystic powers to open a portal, the portal goes haywire and the brothers are sucked into a different version of their home. Soon enough the Rise turtles meet the 2012 turtles in a very dramatic manner in which Donnie and Mikey attempt to find shelter in the nearby sewers.

Or
The Rise turtles meet the 2012 Turtles after being sucked into a portal made from one of Rise Donnie's machines.

(COVER ART BY @neoncolorblocks -- TUMBLER) pls don't sue me :')