Martine Allard as Carmella Robinson (episodes: Carmella Meets The Gooch, Arnold's Songbird)
John Astin (episode: A Haunting We Will Go)
Hoyt Axton as Sam's father (several episodes)

B
Shari Belafonte-Harper (episode: The Older Woman)
Ray Bolger (1986)
Milton Berle (episode: The Bar Mitzvah Boy)

C
Andrew Dice Clay as Crazy Larry (episode: My Fair Lady (or Larry))
Clarence Clemons (episode: So You Want to Be a Rock and Roll Star)
Mindy Cohn as Natalie (episodes: Slumber Party, The Older Man)
Dabney Coleman (episodes: Arnold's Girlfriend (Parts 1 and 2)

D
Nancy Davis (Nancy Reagan) as herself

Abb Dickson (the postman)

E
Krista Errickson (crossover episodes with Hello, Larry)

F

Kim Fields as Tootie (The Girls' School, Slumber Party, Bank Robbery (parts 1 and 2), First Day Blues, The Team)

G
Jami Gertz as Lindsey (1983)
Clarence Gilyard, Jr. as The Student (episode: First Day Blues)
Robin Givens (1986)
Joanna Gleason (crossover episodes with Hello, Larry)
Regi Green as Steve (episode: The Gymnasts)

H
Dorothy Hamill (figure skater) (episode: Family On Ice)
David Hasselhoff (episodes: Hollywood (Part 1 and 2)

I

J
Janet Jackson as Charlene (later had a regular role)
Reggie Jackson (episode: Father and Son Day)
Rachel Jacobs as Arnold's friend Alice (1979) (episodes: Arnold's Girlfriend (Parts 1 and 2)
Anne-Marie Johnson
Ed "Too Tall" Jones (episode: It's Magic)
Gordon Jump (episodes: The Bicycle Man (Parts 1 and 2)

K
Jayne Kennedy (former Miss Ohio) (episode: The Moonlighter)

L
Joey Lawrence as Arnold's friend Joey (episode: Big Brother)

M
Ron Masak (episode: "Sam's New Pal", 1985)
Whitman Mayo (Grady on Sanford & Son) (episodes: The Adoption (Parts 1 and 2)
Kari Michaelson (Katie Kanisky on Gimme A Break) (episode: Little Mother)
Mary Ann Mobley (in episode Teacher's Pet), later had regular role as Mrs. Drummond (last season)
Soleil-Moon Frye (episode: Sam's New Pal)
Howard Morton (Officer Ralph Simpson on Gimme A Break) (episode: Prep School)

N

O

P
La Wanda Page (Aunt Esther of Sanford & Son)
Lance Parrish (former Detroit Tigers catcher) as himself
Tyren Perry as Jennifer (Arnold's Big Strike, The Honorable Arnold J. Jackson), as Phyllis (The Big Bribe)
Julie Piekarski as Sue Ann (from The Facts of Life)

Q

R
Kim Richards (crossover episodes with Hello, Larry)
Jack Riley (several episodes including Goodbye, Dolly and The New Landlord)
Molly Ringwald (from The Facts of Life)

S
McLean Stevenson (crossover episodes with Hello, Larry)

T
Mr. T as himself (episode: Mister T and mister t)

U

V
Jacob Vargas

W
Melanie Watson as Kathy Gordon (4 episodes)
Lisa Whelchel (episodes: The Girls' School, Slumber Party, The Older Man)
Forest Whitaker (episode: A Bully for Arnold)
Donna Wilkes (crossover episodes with Hello, Larry)
Spice Williams as Factory Foreman/woman

X

Y

Z

Other
The 1984 Men's U.S. Olympic Gymnastics team (episode: The Gymnasts)
KITT from Knight Rider (episodes: Hollywood (Parts 1 and 2)