I'm not saying that there was anything wrong with the origin used in the Mirage comics, the live-action films, Next Mutation, the 2003 show, and the 2007 CGI film where Splinter was Hamato Yoshi's pet who mutated and vowed revenge after his owner was killed by the Shredder, but I've always found Splinter more interesting with the mutated Hamato Yoshi origin that he had in the 1987 show, the Archie comic books, and the new Nickelodeon show.
I would really like to know how they will be handling the Turtles' origin in the upcoming 2014 film. I also hate how they're always teasing us in regards to what Splinter is like. We only see a brief glimpse of him in the trailers and his action figure and LEGO minifigure can only give us a vague hint on how he will really look.
The thing is, while I prefer Hamato Yoshi mutating into Splinter, I am not sure if that approach would work in a live-action movie, but that is probably just because I am used to the old movies following the Mirage origin.
I know the trailer had Eric Sachs/Shredder say that he and April's dad created the Turtles, but it IS a very early trailer, and movie trailers have been known to be misleading, so I suggest we take what the trailers say with a grain of salt. I also refuse to believe the rumors that Splinter is April's dad.
The bottom line is I would like your two cents on how Splinter's origin should be in the new film.
I think they're going with the IDW origin, where Hamato and his sons were told by Tang Shen to flee from Oroku Saki, who later found them in New York and killed them, and they were later brought back from the dead in the bodies of a rat and four turtles, where they escaped and found Mutagen spilled on them.