It's Friday!  It's clip time.  What excites me the most is that in one of these clips, there's a Castiel sighting!  Plus, Sam finally gets to do the time travel thing.  It's awesome.  There has been an episode title change.  Here's the synposis courtesy of The CW and Warner Brothers:

The episode, titled "The Song Remains the Same" (fka as "Back to the Future II") will air on Thurs., 2/4 at 9:00 p.m. ET/PT on The CW.

BACK TO THE 70s - When Anna (guest star Julie McNiven) escapes her captors in Heaven and tries to find Sam (Jared Padalecki) & Dean (Jensen Ackles), Castiel (Misha Collins) is suspicious of her motives.  He soon learns that she's gone back in time in a "Terminator-like" plan to stop the Apocalypse by killing the young John & Mary Winchester before the boys are ever born, thus ending the possibility for them to be vessels for Lucifer and Michael.  Also guest stars Matt Cohen as John Winchester, Amy Gumenick as Mary Winchester and Matt Ward as Uriel.  Steve Boyum directed the episode written by Sera Gamble and Nancy Weiner.  

Clip 1

Clip 2