I can only imagine what he really said when describing this.
Bay: Alright...So what if the turtles...were aliens?!
Assistant: Bay, they're mutants, not aliens...
Bay: NO NO NO. Think about it...they'd be more believable if they were aliens! And we can make it edgey like they're...The last of their kind, their home planet destroyed due to a civil war!
Assistant: ...You just want to make more Transform-
Bay: AND THEY TURN INTO MOTORCYCLES! THE FANS WILL LOVE THIS.
Assistant: ...
Bay: Alright...So what if the turtles...were aliens?!
Assistant: Bay, they're mutants, not aliens...
Bay: NO NO NO. Think about it...they'd be more believable if they were aliens! And we can make it edgey like they're...The last of their kind, their home planet destroyed due to a civil war!
Assistant: ...You just want to make more Transform-
Bay: AND THEY TURN INTO MOTORCYCLES! THE FANS WILL LOVE THIS.
Assistant: ...