The gang at the 12th precinct go all out in the hopes that a delusional witness will lead them to a killer on Castle. "That '70s Show" is the 20th episode of the show's sixth season.

Talk about a great undercover look. We almost didn't recognize Detective Kevin Ryan in this get up.

Which do you think is more distracting, Castle's polyester jacket or the collar on that shirt? We're not sure if that outfit should be immortalized or burned.

Did they all get their shades from the same store? Our boys definitely went all out with their '70s looks. Who is your favorite?

We're saving this picture so we can copy Kate Beckett's 1970s look for next Halloween.

Even Alexis is feeling the flower power in "That '70s Show" We wonder what brought her down to the precinct, other than the groovy fashion show.

Has Beckett finally gotten Castle to do the paperwork? Maybe he found the old electric typewriter inspiring. Did they have White Out in the 1970s?

Honestly, we have no words. Except maybe groovy, far out and we hope to catch them on the flip side.

Even Martha gets in on the act in "That '70s Show" We're sure she couldn't resist.

So this is what Beckett's murder board would have looked like in the 1970s. Good thing the Feds haven't shown up with their digital version. That would blow this guy's mind.

We're not sure which is worse. The hair or that mustache. When we finally stop laughing maybe we'll figure it out.

Wow! It looks like everyone at the 12th precinct gets in on the act. Those are some seriously groovy outfits on this episode of Castle.

Whoever Beckett is speaking with, she looks much too young to have murdered someone in the 1970s but she certainly looks upset.

We're not sure how Beckett feels about her new look but we're digging those beads. "That '70s Show" is the 20th episode of the show's sixth season.

No matter what decades she's in, Detective Kate Beckett never fails to look stunning on Castle.