The subtitles are in English with some portugeuse written over top.  Don't worry, it's still easily read and the concept isn't exactly rocket surgery.  It's just outright pure awesome.

So recently a few guys down in Indiana played thru almost all the Mario games all in support of Child's Play. Ever wonder where the name Mario came from? How about Koopa or Wario? Well here are some answers you may have not known. Now you can go on living a normal life having knowledge to those childhood questions.