Most recent roles are only listed by title if they occurred 2011-on. “As Self” is only listed if there are minimal or no other recent appearances. The Fonz and the Happy Days Gang cast noted at the bottom of this post.
Ron Howard (Richie Cunningham): Last known acting role as Narrator in a 2013 episode of Arrested Development; also in The Death and Return of Superman (2011) and From Up on Poppy Hill (US version; 2011); as Director, last in The Dilemma (2011), with Rush (2013) in post-production and Jay-Z: Made in America (2013) in Pre-Production.
Marion Ross (Marion Cunningham): In Heebie Jeebies (2013), Dear Dracula (2012), Handy Mandy (4 episodes 2012), Up All Night (1 episode 2012), SpongeBob Squarepants (1 episode 2011), Keeping Up with the Randalls (2011), Generator Rex (2 episodes 2011); A Reason (2013) in post-production.
Tom Bosley (Howard Cunningham): Died in 2010.
Erin Moran (Joanie Cunningham): Last known acting role in 2010; appeared as Self in a 2012 episode of Celebrity Ghost Stories.
Henry Winkler (Arthur “Fonzie” Fonzarelli): In Newsreaders (1 episode 2013), Adventures of Serial Buddies (2013), Hero Factory (1 episode each 2012 and 2013), Royal Pains (recurring 2010-2012), Robot Chicken (1 episode 2012), Children’s Hospital (recurring 2010-2012), Here Comes the Boom (2012) , Up All Night (1 episode 2012) , Handy Mandy (1 episodes 2012), Batman: The Brave and the Bold (1 episode 2011 as Ambush Bug), Running Mates (2011), Dan Vs. (1 episode 2011), The Dining (2011); Hilliers (2010) in post-production, Larry Gaye: Renegade Male Flight Attendant (2013) in pre-production.
Anson Williams (Warren “Potsie” Weber): Last known acting role in 2009; currently directs episodes of The Secret Life of the American Teenager.
Don Most (Ralph Ralph): In Glee (1 episode each 2011 and 2012) and Chez Upshaw (2012); directed Harley’s Hill (2011); as Self in Good Morning, America (1 episode 2012).
Scott Baio (Charles “Chachi” Arcola): Current regular in See Dad Run (2012); as Self in 2012 episodes (1 each) of The Talk, Watch What Happens: Live, Big Morning Buzz Live, Today; as Self in Celebrity Close Calls (1 episode 2011).
Al Molinaro (Al Delvecchio): Last known acting role in 1992 (as Self in 2005).
Noriyuki “Pat” Morita (Matsuo “Arnold” Takahashi): Died in 2005.
Lynda Goodfriend (Lori Beth Allen-Cunningham): Last known acting role in 1994 (as Self in 2006).
Ted McGinley (Roger Phillips): In 2012 episodes (1 each) of The Mentalist and Sullivan and Son and 2011 episodes (1 each) of Batman: The Brave and the Bold (as Aquaman 2) and Breaking In; also Imaginary Friend (2012), Notes from the Heart Healer (2012), Bad Behavior (2012), Christmas with a Capital C (2011); Road Trip (nd) in post-production.
Cathy Silvers (Jenny Piccalo): Last known acting role in 1996 (as Self in 2005).
Notable Recurring Guest Stars
In some cases other recurring guest stars may have actually appeared in more episodes; however, this list on notability of the characters.
Gavan O’Herily (first Charles “Chuck” Cunningham): Last known acting role in 2009 (as Self in 2010).
Randolph Roberts (second Charles “Chuck” Cunningham): Last known acting role in 1985 (as Self in 2005).
Billy Warlock (Leopold “Flip” Philips): In Discedo (2011).
Crystal Bernard (Krystal “KC” Cunningham): Last known acting role in 2008.
Linda Purl (Ashley Pfister): Recurring guest star on The Office; also Stalked at 17 (2012), True Bold (2 episodes 2012), Homeland (3 episodes 2011).
Heather O’Rourke (Heather Pfister): Died in 1988 at age 12.
Beatrice Colen (Martha Simms): Last known acting role in 1997.
Harris Kal (Bobby): Last known acting role in 1992.
Kevin Rodney Sullivan (Tommy): Last known acting role in 1984; directed a 2011 episode of NCIS: Naval Criminal Investigative Service.
Dennis Mandel (Eugene Belvin): Last known acting role in 2006.
Scott Mitchell Bernstein (Melvin Belvin): No known other acting roles.
Ed Peck (Police Officer Kirk): Died in 1992.
Neil J. Schwartz (Bag Zombrowski): Last known acting role in 1983.
Misty Rowe (Wendy): Last known acting role in 1991 (as Self in 2007).
Suzi Quatro (Leather Tuscadero): Last known acting role in 2007; as Self in The Joy of the Single (2012), Les années Bonheur (1 episode 2012); as Self in 2011 episodes (1 each) of Rage, RocKwiz, Breakfast, the Wright Stuff; soundtrack used in Rage (1 episode 2011) and Red Dog.
Roz Kelly (Pinky Tuscadero): Last known acting role in 1983.
Ellen Travolta (Louisa Arcola): Last known acting role in 2009; as Self in The 9th Annual TV Land Awards (2011) and a 2011 episode of Good Morning America.
Characters played by Penny Marshall, Cindy Williams, David L. Lander, Michael McKean, and Eddie Mekka are more notable from the perspective of the spin-off series Laverne & Shirley and will be covered in a Where are They Now? devoted to that series. Likewise Robin Williams and Mork and Mindy.
The Fonz and the Happy Days Gang Main Cast:
Henry Winkler, Ron Howard, Don Most: See above.
Didi Conn (Cupcake): In Gigantic (1 episode 2011); Didi Lightful (nd) in pre-production.
Frank Welker (Mr. Cool) (due to his already extensive list, video game roles not noted and the cut-off 2012, not 2011): Regular on Scooby-Doo! Mystery Incorporated (as both Scooby-Doo and Fred), The Garfield Show (as Garfield), Transformers Prime (as Megatron), Curious George (as George); semi-regular on Robot Chicken, Futurama; also Batman: The Dark Knight Returns Part 1-2 (2012-2013) , Teenage Mutant Ninja Turtles (1 episode 2012), Big Top Scooby-Doo (2012, as Scooby-Doo and Fred), Frankenweenie (2012), Pound Puppies (1 episode 2012), Madagascar 3: Europe's Most Wanted (2012), Mad (2 episodes 2012), Mirror Mirror (2012), Outback (2012), Cartoon Network 20th Anniversary (2012; as Scooby-Doo).