Teenage Mutant Ninja Turtles: The Newest Brother

What would have happened if something else distracted the Shredder after he'd defeated the turtles before he saw Xever's fish form? Or rather, someone? And, what if this person knew April? Well for one, the turtles would get a new "brother". And for another, Donnie might just stop his attempts to get with April. (OC (Mark) x April, 2012 Version, T rated b/c of added violence.)