Shaggy: Chad Alva
Fred: Michael Vega
Daphne: Bree Olson
Velma: Bobbi Starr
party girl: Lily Labeau
Evan Stone is mentioned on the box, but he appears only briefly in a non-sex role.
Everyone in the cast does a reasonable job in their acting roles, but only Bobbi Starr seems to be really into her part. She seems to really enjoy playing Velma. The character of Daphne seems a bit off, but I attribute that more to the writing than to Bree Olson.
Everyone's great in the sex scenes. All of the scenes are enjoyable, but Bobbi Starr's scenes were my favorites.
Scene 1: Chad Alva and Lily Labeau
Shaggy recounts the story of how he hooked up with a random girl at a party. In the ensuing flashback we get to see Shaggy receive a nice blowjob before proceeding to fuck her in a variety of positions. There's some reasonable chemistry, and the scene is well put together, but for whatever reason it failed to excite me.
Scene 2: Michael Vega and Bree Olson
Unable to contain themselves after hearing Shaggy's story, Fred and Daphne jump into bed, with Shaggy and Velma watching. They really go at it, and the scene is fun to watch. Bree forgets her character when she's excited by the sex, but that's ok. Few porn stars manage to stay in character during sex scenes. Most of the film's anal action occurs in this scene.
Scene 3: Chad Alva and Bobbi Starr
While searching the spooky house for clues, Velma admits to Shaggy that she was really likes him. We get a brief flashback of her masturbating (which is pretty hot, with good camera angles to show off her lovely pussy) followed by a great scene between the two of them. Bobbi Starr really enjoys herself here, but stays in character as Velma throughout.
Scene 4: Bobbi Star and Bree Olson
When a ghost catches the gang in the house, Velma grabs Daphne and convinces her to help "distract" the ghost so the boys can take care of him. The distraction starts out with them making out, but quickly leads to an extended session of oral sex, fingering, and tribbing, as the two girls find out how much they enjoy lesbian sex. This was a very hot scene, with two very pretty women who seem to enjoy working together. Luckily for us, it takes a good twenty minutes before Fred finally gets around to punching the bad guy, so we get a good long look at the lovely ladies. I think this was the longest scene in the film, and while it seems odd plot-wise for it to go on so long, I'm not complaining.
Scene 5: Chad Alva, Bobbi Star, Michael Vega, and Bree Olson
Even before they've managed to catch the villain, the four heroes become distracted and have an orgy in the middle of being chased by the bad guy. Well, it's more of a swinging scene than an orgy, as it mostly involves the two couples having sex next to each other. They swap partners a few times, and there are some very short sequences where three of them play together for awhile, but most of the time it's two couples side-by-side. The editing is good, so it works out pretty well. This is the second scene to feature anal, but once again only Bree Olson takes it up the ass. Bobbi Starr doesn't participate in any anal sex.
Personally I think it would have been great if Fred and Shaggy got it on in this scene, but this is mainstream porn so the typical double-standard applies: while two girls making out is allowed in hetero porn, the idea of two dudes together is completely off-limits.