Cassandra is a great friend to Xander. That's why she told their professor that Xander couldn't make it to class cause he was sick. The professor knows the true story (Xander got in a fight) and now Cassandra feels like a jerk. Xander wants to express his thanks to Cassandra for being a great friend by going down on her...
Video from Cassandra Nix in Naughty America (Cassandra Nix and Xander Corvus in Fast Times)
Pictures from Cassandra Nix in Naughty America (Cassandra Nix and Xander Corvus in Fast Times)