All 122 actors in both ER and How I Met Your Mother
122 actors have appeared in both ER and How I Met Your Mother, across 539 episodes. The most-credited is Joe Nieves, Tony Dejesu in ER and Carl in How I Met Your Mother.
| Actor | In ER | In How I Met Your Mother | Eps | Eps |
|---|---|---|---|---|
| Joe Nieves | Tony Dejesu | Carl | 1 | 21 |
| Marshall Manesh | Babu | Ranjit | 1 | 19 |
| Busy Philipps | Dr. Hope Bobeck | Rachel | 14 | 1 |
| Joe Manganiello | Officer Litchman | Brad Morris | 4 | 7 |
| Kal Penn | Narajan | Kevin | 1 | 8 |
| Michael Gross | John "Jack" Carter | Alfred Mosby | 6 | 3 |
| Frances Conroy | Becky Riley | Loretta | 2 | 6 |
| J.P. Manoux | Dr. Dustin Crenshaw, Mime | Not Moby | 24 | 1 |
| Monique Edwards | Callie | Producer | 1 | 4 |
| Kevin Michael Richardson | Patrick | Stan | 3 | 1 |
| Cristine Rose | Mrs. Martinez | Virginia Mosby | 1 | 6 |
| Bruce Gray | Carter Board member, Dr. Munch | Yuthers, Senior Partner | 2 | 3 |
| Brad Grunberg | Masked Man | Bruno | 1 | 1 |
| Dan Lauria | Rick Simpson | Nolan | 1 | 1 |
| K Callan | Kelly Robinson | Grandma Lois | 1 | 3 |
| George Cheung | Mr. Chen, Mr. Fong | Korean Elvis | 4 | 1 |
| Anne Dudek | Paula Gamble | Natalie | 1 | 2 |
| Ernie Hudson | Colonel James Gallant | Ernie Hudson | 2 | 1 |
| Jayden Lund | Workman #2 | Bill | 1 | 2 |
| Judith Drake | Greta | Bernice | 1 | 3 |
| Michael Kagan | Chuck Arteburn | Joel Adams | 1 | 3 |
| Alexis Krause | Mallory | Carol | 1 | 1 |
| Caroline Lagerfelt | Andrea | Bridal Shop Lady | 1 | 1 |
| David Grammer | Clerk | Captain Dearduff | 1 | 2 |
| Robert Wisdom | Dr. Hammond | McCracken | 1 | 1 |
| Sergey Brusilovsky | Adrian, Boris Nadinovitz | Tailor | 2 | 1 |
| Tyler Peterson | Tate Udecker | Young Marshall | 1 | 2 |
| Connie Sawyer | Kathy Brennan, Second Old Lady | Old Lady | 2 | 1 |
| Ewan Chung | Chiu | Carol, Co-Worker | 1 | 2 |
| Lawrence Mandley | Jackson, Maintenance Man | Cab Driver #1 | 2 | 1 |
| Marjorie Lovett | Colostomy bag lady | Aunt Muriel | 1 | 2 |
| Andrew Astor | Tyler | Addison | 1 | 1 |
| Carlease Burke | Policewoman | WPD Worker | 1 | 1 |
| Frank Clem | Turner | Hick | 1 | 1 |
| Joey Diaz | Grocery Store Clerk | Angry New Yorker | 1 | 1 |
| Judy Greer | Tildie Mulligan | Royce | 1 | 1 |
| Kelly Perine | Collins | Fred | 1 | 1 |
| Sharon Madden | Risberg | Milly | 1 | 1 |
| William Schallert | Mitchell Jennings | Brady | 1 | 1 |
| Michael Earl Reid | Bennet Owens | Postmaster General | 2 | 1 |
| Stefanie Black | Tiffany | Kelly | 1 | 2 |
| Charlie Stewart | Albert | Kenny | 1 | 1 |
| Dale E. Turner | Daniel Harrison | Professor Calzonetti | 1 | 1 |
| Diane Salinger | Sophie's Mom | Dr.Birnholz-Vazquez | 1 | 1 |
| Earl Billings | Ray Jamison | Officer McNeil | 1 | 1 |
| Jae Suh Park | Mary Tan | Crystal | 1 | 1 |
| Maggie Wheeler | Amy Kellerman | Margaret | 1 | 1 |
| Michael McCafferty | Father | Cabbie | 1 | 1 |
| Michael Spellman | Dr. Jim Babinski | Adam | 3 | 1 |
| Pat Crawford Brown | Mrs. Votey | Thelma | 1 | 1 |
| Peter MacKenzie | Mr. Pasbalas | Mr Horvath | 1 | 1 |
| Richard Gant | Mr. Lipson | Judge | 1 | 1 |
| Ryan Michelle Bathé | Miss Evelyn | Michelle | 1 | 1 |
| Petrea Burchard | Judge Amoroso | Female Gallery Patron | 2 | 1 |
| Barry Finkel | Vank | Crazy Man | 1 | 1 |
| Bianca Lopez | Monica | Gennie | 1 | 1 |
| Brenda Ballard | Barb Weston | Fran | 1 | 1 |
| Donna Pieroni | Wuss | Maid | 1 | 1 |
| Elizabeth Bogush | Debra Strickland | Amanda | 1 | 1 |
| Gary Kraus | CJ | Wedding Videographer | 1 | 1 |
| Jack Shearer | Hal Grunwald | Cab Driver | 1 | 1 |
| Jamison Yang | Shuang Tseng | Concerned Guy | 1 | 1 |
| Joe O'Connor | Mr. Scott | Cassie's Dad | 1 | 1 |
| John C. Moskoff | Len Weston | Herm | 1 | 1 |
| Marcus Folmar | Foreman | WPD Driver | 1 | 1 |
| Michael Hagiwara | Steve Sakabu | Mr. Li | 1 | 1 |
| Nick Jaine | Scrub Nurse | Sudeep | 1 | 1 |
| Patricia Belcher | Ward Nurse | Receptionist | 1 | 1 |
| Tom Virtue | Pares | Minister | 1 | 1 |
| Vanessa Vander Pluym | Vanessa | Janine | 1 | 1 |
| Wayne Lopez | Benitez | Referee | 1 | 1 |
| Cailey Blair Jones | Rose Nichols | Little Girl #1 | 1 | 1 |
| Chris Tallman | Burt Mulligan | Mark | 1 | 1 |
| Darryl Sivad | Colin | Officer Roque | 1 | 1 |
| Dean Chekvala | Mugger | Hippie Dude | 1 | 1 |
| Gary Riotto | Cousins | Waiter #1 | 2 | 1 |
| Irene Roseen | Inez | Old Gyspy Woman | 1 | 1 |
| Jim Jansen | Neonatologist | Doctor | 1 | 1 |
| John Rosenfeld | FBI Agent Robert Clayton | Guy | 1 | 1 |
| Keegan-Michael Key | Witkowski | Obnoxious Man | 1 | 1 |
| P.J. Marino | Officer Jaeger | Bartender | 1 | 1 |
| Stephanie Faracy | Angie | Rhonda | 1 | 1 |
| Terrell Lee | Russomante | Bouncer | 1 | 1 |
| Bruno Amato | Sheriff | Cop | 1 | 2 |
| Brenda Isaacs-Booth | Sandra Perry | Tracy | 1 | 1 |
| Brian David Jones | Jackson | Co-worker #2 | 1 | 1 |
| Buck Kartalian | Lloyd Frick | Henry | 1 | 1 |
| Cal Gibson | Kim Tadlock | Ryan | 1 | 1 |
| Di Koob | Sophia Van Brummelen | Lauren | 1 | 1 |
| Michael Edwin | Drunk Man | Eddie | 1 | 1 |
| Michael Mantell | Mr. Spencer | Ben | 1 | 1 |
| Roz Witt | Saleswoman | Mom | 1 | 1 |
| Taira Soo | Jordan | Nurse | 1 | 1 |
| Ambrit Millhouse | Mother | Jill | 1 | 1 |
| Austin Majors | Lucas Shore | 12-Year-Old Matthew | 1 | 1 |
| Jarrod Crawford | David "Diamond Z" Zachary | Guy | 1 | 1 |
| Jennifer Lothrop | Supervisor | Woman | 1 | 1 |
| Jeremy Glazer | Med Student David | Bruce | 1 | 1 |
| Ria Pavia | Stanford Candidate | Gloria | 1 | 1 |
| Rob Evors | Gary | Bradley | 1 | 1 |
| Tahmus Rounds | Colby | Guitar Mom | 1 | 1 |
| Bette Rae | Mrs. Gottschuck | Mrs. Berkelheimer | 1 | 1 |
| Hal Havins | Jacobi | Cab Driver | 1 | 1 |
| Johnny Palermo | Officer Scanaloni | Cafe Guy | 1 | 1 |
| Jonathan Morgan Heit | Jessie | Boy #1 | 1 | 1 |
| Marianne Muellerleile | Mrs. Jarnowski | Meredith | 1 | 1 |
| Mary Ann Jarou | Dora | Jenny | 1 | 1 |
| Michelle Noh | Kate | Claire | 1 | 1 |
| Nancy Stone | Assistant | Sketch Artist | 1 | 1 |
| Ping Wu | Mr. Cheung | Old Man | 1 | 1 |
| Valorie Hubbard | Mrs. Bulowski | Gladys | 1 | 1 |
| Michael C. Mahon | Joe | Grumpy Man | 2 | 1 |
| Charles Rahi Chun | Ben's Dad | Mr. Park | 1 | 1 |
| Kim Estes | Lieutenant Higgins | Judge #1 | 1 | 1 |
| Linda Porter | Inga Paulson | Muriel | 1 | 1 |
| Steve Tom | MacPherson | Kelly's father | 1 | 1 |
| Harry S. Murphy | Dr. Hamill | Reverend Platt | 1 | 1 |
| Floyd Van Buskirk | Workman | Cab Driver #2 | 1 | 1 |
| Steve Seagren | Zimmer | Bailiff | 1 | 1 |
| Kathleen M. Darcy | Judy | Wedding Guest #2 | 1 | 1 |
| Camille Guaty | Mia | Lisa | 1 | 1 |
| Christopher Darga | Wilson | Bus Driver | 1 | 1 |
Cast data from TVmaze, licensed CC BY-SA 4.0.