Järegård had a taste for villainious and dark characters, and he enjoyed playing them. But he also had a very lyrical and soft side to him as an actor, something he showed in the TV-production of Hans Christian och sällskapet (where he plays a village priest who suffers a great personal tragedy as his wife loses her mind after having a baby) and in the TV adaptation of Birger Sjöberg's Frida och hennes vän (based on Sjöberg's Frida's Book) where he plays the light-hearted, daydreaming early 1900s love-struck suitor of Frida. Adding to the fact that Järegård also had a beautiful and expressive singing voice (he performed in a number of stage musicals during his career) gave him an incredible range and versatility as an actor. He originated the role of Guido in the first European staging of the musical Nine, for example (Oscarsteatern, 1983). His distinct and original voice (with traces of the unmistakable Skåne-dialect) also made him a much appreciated and beloved narrator of children's cartoons and audio books. Particularly popular are his audio book recordings of Roald Dahl's Charlie and the Chocolate Factory and Robert Louis Stevenson's Dr Jekyll and Mr Hyde.
Järegård gained international attention when he took on the role of Doctor Helmer in Lars von Triers highly acclaimed mini-series Riget and Riget II (aka The Kingdom I & II). He also appeared in von Trier's Europa. He participated in about 20 movies and 40 TV productions: aside from the Riget-series, some of his greatest roles are in the Skånska mord-series, in the 1975 Hasseåtage comedy Släpp fångarne loss, det är vår! (Release the Prisoners to Spring), in the 1962 cult movie Raggargänget, in Kådisbellan (aka The Slingshot) in 1993 and as the pompus old drag queen Ragnar Rönn in TV-theatre production Cheek to Cheek (written and directed by Jonas Gardell), 1997.
Järegård married Karin Nordström (b. 1923) in 1950 . They had one son, Johannes.
Järegård was a very colourful theatre personality who loved to stand out and celebrated originality. He loved clothes and Italian designers and was picky with designer labels in private - only the best would do. He was of the old belief that as an actor you not only represent yourself as a public person but also the theatre and the art as a whole; as being part of a public institution there for people; and therefor it is an actor's responsibility to "scrub up".
In his director's commentary on the DVD release of Europa, Lars von Trier says that Järegård was difficult to work with, frequently sulking and making outrageous demands such as insisting on staying in one specific room in a specific hotel of his choice. He also says that Järegård was a compulsive scene-stealer who could no help pulling focus even when he was supposed to be in the background of a scene. Von Trier claims that he eventually 'trained' Järegård by rewarding him with cigars for good behaviour. However, von Trier also refers to the actor as "dear Ernst-Hugo" and says that he misses him terribly.
A famous quote from Järegård is "When I get up at night to grab a sandwich it only takes a ray of light from the fridge lamps for me to start acting."