Frank Oz was one of Jim Henson's closest creative partners, beginning in 1963. Oz played Bert to Henson's Ernie on Sesame Street, and he also performed Cookie Monster and Grover. In 1976, Oz created many of the core characters for The Muppet Show, including Miss Piggy, Fozzie Bear, Animal and Sam the Eagle, and he continued to perform these characters in the Muppet movies and TV specials. Henson and Oz collaborated on the 1982 film The Dark Crystal, directing as a team.
In the mid-1980s, Henson and Oz began to pursue separate creative projects, outside of the Muppets. Henson produced fantasy film and television projects -- Labyrinth (1986), The StoryTeller (1988) and The Witches (1990). Meanwhile, Oz began a career of directing comedy films -- Little Shop of Horrors (1986), Dirty Rotten Scoundrels (1988) and What About Bob? (1991).
In 1989, Henson created a new Muppet TV series, The Jim Henson Hour, with "MuppeTelevision" segments filmed in a studio in Toronto. Oz, who was working on film projects at the time, participated in the show by filming solo segments with Fozzie Bear and Miss Piggy. Fozzie was seen in New York City in episode 103, and Oz performed both Miss Piggy and Fozzie in Los Angeles for a half-hour segment in episode 105, Miss Piggy's Hollywood.
In An Evening with Jim Henson and Frank Oz, Oz stated that he only did a few days of work on Sesame Street and The Jim Henson Hour in the past year because "it's an issue of scheduling. I do a lot of movie work now. It's hard to make the schedule work." Later Henson jested that he lost his best puppeteer to a directing career.
In a 2007 interview, Oz explained why he distanced himself from Muppet performing:
1990s Muppet projects
After Jim Henson's death in 1990, his 27-year-old son Brian was named President, Chairman and CEO of The Jim Henson Company. Brian planned to revive the Muppet franchise with a series of movies, beginning with the 1992 film The Muppet Christmas Carol. Oz was working on another movie at the time, but supported the Muppet project by performing Miss Piggy, Fozzie Bear, Animal, Sam the Eagle, and other incidental characters in several scenes and served as an executive producer for the film.
The gag reel for The Muppet Christmas Carol includes a possible reference to Oz's limited time on the set. In one outtake, Gonzo and Rizzo the Rat (performed by Dave Goelz and Steve Whitmire) are sitting on a shelf next to a bust of William Shakespeare. Noticing a resemblance to Oz's hairline, Rizzo says, "Hey, it's Frank Oz!" Gonzo says, "Whoa, they've coated him with plaster!" and tries to get "Frank's" attention: "Frank, speak to us!" "Huh," Rizzo says, shaking his head. "As usual."
In the mid '90s, Oz was able to participate in smaller Muppet projects such as the albums Muppet Beach Party and Kermit Unpigged, and the direct-to-video Muppet Classic Theater performing Miss Piggy, Animal, and Fozzie Bear.
In the late '90s, Oz's character Sam the Eagle made a guest appearance on episode 318 of The Animal Show. Oz was not available to puppeteer the character, so someone else performed the character on set and Oz looped the voice in post-production.
In 1996, Oz was unable to participate in the majority of the filming of Muppet Treasure Island because he was directing at the time. Kevin Clash performed Oz's characters on set, and Oz looped the dialogue in post-production. Oz was also the executive producer of that film. Oz was however available to perform Fozzie Bear, Miss Piggy, and Animal in new video material produced for a smaller project, the Muppets Inside CD-ROM computer game, released the same year.
For the 1996 TV show Muppets Tonight, Oz performed Miss Piggy, Fozzie Bear, Animal, and Sam the Eagle in a limited number of episodes, although other puppeteers filled in at times. Miss Piggy appeared with many of the guest stars, including Michelle Pfeiffer (episode 101), Garth Brooks (episode 102), Billy Crystal (episode 103), Whoopi Goldberg (episode 109) Martin Short (episode 110) and Pierce Brosnan (produced in the first season, but aired as Episode 204). Oz also performed several one-shot characters, such as a stagehand (episode 101), a lion (episode 103), and others. Oz's involvement was even more limited in the show's second season.
For the 1999 film Muppets from Space, Oz was again unavailable for most of the filming; Peter Linz performed Miss Piggy on set, John Kennedy performed Fozzie Bear and Sam the Eagle, Rickey Boyd performed Animal, and again Oz looped the dialogue in post-production. 
In the late 1990s, Oz's directing schedule was continuing to limit his time on Sesame Street and other Muppet projects. Although at times he'd dub to other puppeteers (as with the Muppet movies), it was decided to find replacement puppeteers for his major characters. Oz himself chose who he wanted to take each character; the bulk of his roles went to Sesame Street puppeteer Eric Jacobson, who began performing Bert in 1997 on a semi-regular basis, and started performing Grover the year after (and soon became their principal performer). Despite this, Oz returned to perform Bert, Grover, and Cookie Monster for the 1999 film The Adventures of Elmo in Grouchland. Veteran Muppet performer David Rudman took over Cookie Monster in 2001.
In an interview, Oz said on the subject, "What happened was, I was off directing for six months and I can’t say [to the Henson Company], "You can’t use [those puppets] for six months." So I had to give it up, but I do miss it, yeah."
Oz commented on the performer shift:
Oz continues to return to Sesame Street, at least once for almost every season; recent instances include Mr. Draper in a Mad Men parody (2009), Keith Heartburn in a Deadliest Catch parody (2011), Grover as Spider-Monster (2011), Clucky Luciano in a "Boardwalk Empire" parody (2012), as well as Grover singing "I Am Special".
Departure from the Muppets
In the early 2000s, Oz retired from performing Miss Piggy, Fozzie Bear, Animal, and Sam the Eagle.
In December 2001, Eric Jacobson secretly debuted as Miss Piggy's new performer in a video greeting shown at the MuppetFest fan convention. Jacobson made his first major Muppet production debut performing Fozzie Bear, Miss Piggy, and Animal in the 2002 TV-movie It's a Very Merry Muppet Christmas Movie. Jacobson took over the role of Sam the Eagle starting in 2005 with The Muppets' Wizard of Oz.
Evidently, Frank Oz was offered the chance to perform in the 2011 film The Muppets, despite the fact that as noted, he had retired from Muppet performing. In Fall 2011, when speaking of the early script of the then upcoming film, Oz was quoted in a UK article as saying:
Oz stated in the same interview that:
Oz's quote about being dissatisfied with the movie's early script was soon publicized, picked up by several U.S. websites and bloggers, combined with unsourced claims that some of the film's Muppet performers were also unhappy with the movie. Since Oz's Muppet retirement in 2000 was relatively quiet, some of these authors were under the impression that his dislike of the early script was the reason for his departure from the Muppets, even though his true departure from performing with the Muppets was almost ten years prior.
In a July 2012 interview, Oz stated;
When asked if he would want to ever work with the Muppets again in a sequel or a TV series, he said:
In a 2015 interview, when asked about whether he would want to return, he said, "I’m not asked to go do it [because] they have other people doing [the characters and voices] now, and they’re satisfied. But I would love to go back and do it for a short period of time, yeah."
- ↑ Oz, Frank August 7, 2007 interview
- ↑ Tough Pigs Youtube interview: Kevin Clash Part 1 of 2
- ↑ Youtube Interview with Peter Linz
- ↑ Film Review Online: Sesame Street’s 40th Anniversary – Puppeteers Eric Jacobson & David Rudman
- ↑ Glamour interview
- ↑ Oz, Frank Sesame Street: A Celebration - 40 Years of Life on the Street Page 130
- ↑ 7.0 7.1 Metro
- ↑ The Hollywood Reporter
- ↑ 9.0 9.1 Collider.com
- ↑ Glamour interview