Paul Haenen is a well-known comedian in the Netherlands and also provides the voices of Bert, Grover and other minor characters on Sesamstraat, the Dutch co-production of Sesame Street, since Sesamstraat's first season in 1976.
Hellen Huisman (born 26 March 1937 in Amsterdam, Noord-Holland - died 29 January 2012 in Blaricum Noord-Holland) was a voice actor who did voiceover work on Sesamstraat, the Dutch co-production of Sesame Street.
He also performed the voices of Hard Head Henry Harris, and Oscar in the song "Swamp Mushy Muddy", one of the few Oscar appearances on Sesamstraat in that era.
On the Dutch version, Sesamstraat, the Yip Yips are called "Sjoerd and Hendrik Marsman", referring to the early 20th-century poet Hendrik Marsman.