'' with
Richard Nixon following a performance of the Tony Award-winning musical in the East Room of the White House (1971) Daniels began his career as a member of the singing Daniels family in Brooklyn. He made his television debut as part of a variety act (along with other members of his family) in 1943, on NBC, then a single station in New York. He made his Broadway debut in 1943 in
Life with Father, and remained a busy Broadway actor for decades afterwards. His Broadway credits include roles in
1776,
A Thousand Clowns,
On a Clear Day You Can See Forever, and
A Little Night Music. He received an
Obie Award for
The Zoo Story (1960). Daniels's motion picture debut was as a school principal in the 1963 anti-war drama film
Ladybug Ladybug. In 1965, he reprised his Broadway role as a child welfare worker in the screen version of
A Thousand Clowns. In 1967 he appeared in
The Graduate as the father of
Dustin Hoffman's character. In 1969, Daniels starred as
John Adams in the Broadway musical
1776; he also appeared in the
film version in 1972. Two years later, he co-starred in
Richard Donner's telefilm
Sarah T. - Portrait of a Teenage Alcoholic. In 1978 and 1979 he again reprised his role as the outspoken John Adams in the films
The Bastard and
The Rebels, again about the American Revolution, without seeming to ever break character. Daniels's first network television appearance came in 1952 when he portrayed the young
John Quincy Adams, eldest son of John and Abigail Adams in the
Hallmark Hall of Fame drama
A Woman for the Ages. In 1976, he reprised the role as the middle-aged and elder John Quincy Adams in the acclaimed
PBS miniseries
The Adams Chronicles. He starred in the short-lived series
Captain Nice as police chemist Carter Nash. He appeared as acid-tongued Dr. Mark Craig in
St. Elsewhere from 1982 to 1988, for which he won two Emmy awards. Concurrently, he provided the voice of
KITT in
Knight Rider from 1982 to 1986. Daniels said in 1982, "My duties on
Knight Rider are very simple. I do it in about an hour and a half. I've never met the cast. I haven't even met the producer." He reprised the role of KITT in the 2015 Lego-themed action-adventure video game
Lego Dimensions. Daniels portrayed strict but loving educator
George Feeny at John Adams High School in
Boy Meets World from 1993 to 2000. In addition to the previously mentioned 1967 superhero sitcom
Captain Nice, he was a regular on the 1970s TV series
Freebie and the Bean and
The Nancy Walker Show. A familiar character actor, he has appeared as a guest star on numerous TV comedies and dramas, including
Soap,
The Rockford Files,
Quincy, M.E.,
Kolchak: The Night Stalker, and many others. In 2012, Daniels appeared in the ninth season of ''
Grey's Anatomy'' as Dr. Craig Thomas, an unlikely mentor to the character of Dr.
Cristina Yang played by actress
Sandra Oh. His character, Dr. Thomas, died in the operating room while performing a procedure to repair a heart defect midway through the season, which forced Yang to move back to Seattle. In 2014, Daniels reprised his role as Mr. Feeny in the pilot episode of the
Boy Meets World spinoff,
Girl Meets World. He cameoed in the final scene, praising the adult Cory Matthews for his parenting. He made additional appearances in the second and third seasons. In early 2023, he completed filming of the role of King Henry VI in the upcoming "Richard III". On October 14, 2025, at 98 years old, he appeared as a surprise guest on
Dancing with the Stars. ==Personal life==