How many people have been test subjects on the Sattelite of Love?

In order of appearance:

1. Joel Robinson
   Test subject between the pilot (KTMA-00- The Green Slime) e S05E12- Mitchell.

   
   _{Joel Robinson as he appeared in S03E03- Pod People}

2. Crow T. Robot
   Test subject between KTMA-01- Invaders from the Deep e S10E13- Diabolik.
   Joel was alone in the theater during the pilot so he wasn't technically a test subject at that point, though he did appear in the episode, unlike Tom Servo.

   
   _{Crow T. Robot as he appeared during the Season 7 intro}

3. Tom Servo
   Test Subject between KTMA-02- Revenge of the Mysterons from Mars e S10E13- Diabolik.
   As mentioned above, Tom Servo didn't technically appear in the pilot episode, though a vaguely similar looking robot called "Beeper" did (in the host segments only):
   

   
   _{Beeper as seen in O Slime Verde}

   Trace Beaulieu who voiced and operated Crow T. Robot during the first 8 series did not appear in Invaders from the Deep, and instead Josh Weinstein (who voiced and operated Tom Servo for the first 2 seasons) played Crow T. Robot and therefore Tom Servo was absent, first appearing as a test subject the next episode:

   
   _{Tom Servo, absent from a rare Invaders of the Deep clip}

   
   _{Tom Servo as he appeared in the Season 7 intro}

4. Cigano
   Sort of. Gypsy joined Joel & The Bots in the theater for S04E12- Hercules And The Captive Women, though she got bored and left after 5 minutes:

   
   _{Gypsy shown at the left of the theater during Hercules And The Captive Women}

   She was also shown in the theatre during the KTMA season intro, though never during the episodes:

   
   _{The original design for Gypsy shown in the theatre during the KTMA opening}

5. Timmy
   In S04E16- Fire Maidens of Outer Space, Joel & The Bots are visisted by a strange creature apparently from Crow's imagination, it's an exact copy but black, and eventually he begins playing tricks on everyone. Several times he shows up in the theater to watch the movie and annoy the gang:

   
   _{Timmy in Fire Maidens of Outer Space}

6. Mike Nelson
   Test subject between S05E13- The Brain That Wouldn't Die e S10E13- Diabolik.
   

   
   _{Mike as he appeared in the season 5 intro}

7. Mirror Universe Clayton Forrester

8. Mirror Universe TV's Frank
   In S06E11- Last of the Wild Horses, the Mads perform a matter transfer experiment which winds up with Mike & The Bots in a Mirror Universe, where Captain Mike and Yeoman Crow are forcing Clayton Forrester and TV's Frank to watch bad movies, and the first third of the episode features them riffing the movie:

   
   _{Clayton Forrester and TV's Frank watching Last of the Wild Horses}

9. Eddie Nelson
   In S08E21- Time Chasers, to fit in with the storyline of the movie, Crow goes back in time and tries to warn Mike not to take the job at Deep 13 which will lead to him getting marooned in space. Upon his return, Crow discovers that all that's changed is now instead of Mike Nelson, they've got his foul-mouthed, beer-swilling asshole brother, Eddie Nelson who riffs the middle third of the film:

   
   _{Eddie Nelson in Time Chasers}

10. Pearl Forrester
    The final test subject was Pearl Forrester, in S09E13- Quest of the Delta Knights she's disappointed that she's been showing Mike terrible movies for 2 years with no real results, so they switch places and Pearl watches the first third of the movie with them to try and work out how best to torment him in the future:

    
    _{Pearl Forrester in Quest of the Delta Knights}

So all together, there were 10 different test subjects. There were also a couple of visitors to the theater who didn't actually Assistir any part of the movie:

1. Fred "Eggs" Eggleston
   After Pearl has finished her investigation of the theater, she brings in "Eggs" from Facilitech to fix the Pain Leakage which has stopped Mike & The Bots from experiencing the Deep Hurting Pearl desires from these movies:

   
   _{Fred "Eggs" Eggleston in Quest of the Delta Knights}

2. Giant Servo
   No final de S10E04- Future War, Mike starts making some shadow-puppets, and out of the blue a giant Servo shadow appears, which is turns out isn't being cast by Mike or Servo:

   
   _{Giant Tom Servo in Future War}