Wolfcastle is a veteran of many violent action movies, most notably the McBain series (unrelated to the 1991 action film by the same name). It is frequently suggested that his career is on the decline since a movie featuring a "magic ticket" similar to Last Action Hero. He battles frequently with weight issues, though tries to pass it off as something he is doing for a role. His films are sometimes critical failures, as Jay Sherman introduced Wolfcastle in an interview on his TV show as "star of the reprehensible McBain movies", including McBain: Let's Get Silly, featuring the character performing standup comedy in front of a brick wall for an hour and a half. It cost $80 million.
According to various Simpsons episodes, Wolfcastle began his acting career as a child in Austria, appearing on long television commercials advertising bratwurst. At roughly the same time, he began experimenting with bodybuilding, and his physique earned him a starring role in several gay pornography films, shelves of which were seen by Homer during one of Wolfcastle's debt-induced garage sales. He was also the primary actor on advertisements for "PowerSauce Bars"; bars claiming to boost muscle growth, but which were in fact a mash of apple cores and Chinese newspapers. Rainer Wolfcastle is an Anti-Semite as revealed in Today I Am a Clown.
The name "Rainier" is the French variant of Rainer, a given name common in Germany and Scandinavian countries (as Ragnar). Also, "Rainier" is a common reference to Mt. Rainier, a large mountain within view of Seattle, Washington. Most Simpsons character names come from streets and landmarks near Portland, the hometown of Simpsons creator Matt Groening.
Rainier Wolfcastle has, in different Simpsons episodes, been a presenter at the Academy Awards, a spokesperson for the PowerSauce energy bar, a celebrity judge in radio station KBBL's contest "How Low Will You Go" (along with Krusty the Klown and Madeleine Albright), hosted a short-lived talk show, and appeared on Inside the Actors Studio with James Lipton (in which he shoots Lipton after getting into character as McBain). He was married to Maria Quimby in the past, and his daughter Greta dated Bart in the episode, "The Bart Wants What It Wants". He also was co-owner of a Planet Hollywood spoof, along with "Chuck Norris, Johnny Carson's third wife, and the Russian mafia".
Apart from the McBain series, Wolfcastle also played Radioactive Man in an ill-fated live-action movie version of the comic book series. Wolfcastle has also ventured into comedic roles; in one episode he carries Homer in an oversized Snugli for babies, remarking, "I used it to carry Rob Schneider in the movie My Baby is an Ugly Man." His other films include Help, My Son is a Nerd, Mrs. Mom, Frankenberry: The Movie, I Shoot Your Face, I Shoot Your Face Again and Diaper Genie. (The last one was actually referenced by Arnold Schwarzenegger in The Simpsons Movie.)
Wolfcastle has campaigned as Republican Mayoral candidate and as a supporter of Sideshow Bob for Mayor.
Hints that Wolfcastle may have some anti-Semitic or Neo-Nazi views derives from Schwarzenegger having had to disavow Nazi sympathies due to his father Gustav Schwarzenegger's onetime Nazi Party membership.
When Krusty the Clown says, "I thought I was a self-hating Jew, but it turns out that I'm just an anti-semite" and nearby Wolfcastle enthusiastically responds, "We have so much to discuss". His lead-in announcer on "Up Late with McBain" dresses in a full SS uniform, complete with Nazi armband, and introduces himself as an Obergruppenführer, which was a high ranking officer in the SA and later the SS. In the episode "See Homer Run", in a stump speech he refers to himself as being, among other things a "...son of a Nazi..". However, in one of his films, after saving UNICEF supplies from a doomed transport plane, he afterwards leaps onto one of the "Commie-Nazi" enemy jet fighters, pops open the cockpit, and snaps the neck of the enemy leader who appears to look like Hitler.
Despite his aforementioned involvement in the gay porn industry, Rainier himself may also be homophobic, as evidenced by his accusing the entire audience of the "Up Late with McBain" show of being homosexuals after they booed him for describing his band leader's outfit as making him "look like a homosexual".