Hey, It's That Guy!: In the last season episode "Medieval Crimes," you'll spot Josh Holloway (aka Sawyer from LOST) as part of a cheesy Ren-Faire restaurant gang that robs jewelry stores. It was one of his first credited TV roles.
In the episode "Last Hope", a young Mila Kunis appears as one of the troubled kids at the Ranger Camp.
In the two-part episode "Lucas", the titular AIDS-suffering child is played by Haley Joel Osment.
Sting appears as a drug dealing biker antagonist in the episode "Unsafe Speed."
Hey, It's That Voice!: Cam Clarke is everywhere in this show. Usually he's just a background voice on the radio or TV, but occasionally he dubs over other characters when they're off screen. One time he actually dubbed a villain who was on screen, which created a huge dissonance the next time you hear the guy and he has a voice that actually looks like it would come out of him.