Danny Elfman and Jenna Elfman are not related by blood. Danny Elfman is a highly celebrated film score composer, known for his work on numerous films such as "Batman," "Spider-Man," and "The Simpsons." On the other hand, Jenna Elfman is an actress who has appeared in popular TV shows such as "Dharma & Greg" and films such as "Krippendorf's Tribe."
While the two share a last name, it is not a common surname, and the likelihood of them being related is low. This can be further confirmed by conducting genealogy research, which would show the family trees of both individuals and any connections they may have.
It is worth noting that Danny Elfman's father was Jewish and his mother was of French-Canadian descent, while Jenna Elfman's ancestry is predominantly Czech. This further emphasizes that they are not related by blood.
In conclusion, based on the information available and lack of familial connections, it can be stated that Danny Elfman and Jenna Elfman are not related.