Puppeteer and voice actor Jerry Nelson may be virtually unknown in the mainstream, but plenty of children (and, yes, some adults) have loved the character he portrayed for many years on PBS' Sesame Street: Count von Count.

Nelson, 78, died Thursday, according to news on a Muppets tribute site, Canada's CBC News reports. No cause of death has been disclosed yet.

In addition to bringing the friendly, numbers-obsessed purple vampire to life, Nelson also played Gobo on Fraggle Rock. Nelson teamed up with Muppets creator Jim Henson in the '60s and joined Sesame Street in the '70s, working throughout on many Muppets movies and serving as a co-producer on Fraggle Rock.

By 2004, Nelson had retired from puppeteering, but continued to voice The Count and other Sesame Street characters until his death.