Harris was a main character on the original series “How I Met Your Mother,” which ran for nine seasons on CBS starting in 2005. He earned four Emmy Award nominations for his performance as serial womanizer Barney.
In the spinoff series, Hilary Duff stars as Sophie, who Harris returned to help look for the father she had never met.
The show also stars Tien Tran, Suraj Sharma, Christopher Lowell, Francia Raisa, Tom Ainsley and Kim Cattrall.
Last season Cobie Smulders, who played Robin in the original series, also made a return.
Hulu aired the two-episode mid-season finale of “How I Met Your Father,” on March 28. After a short break, it will continue the 20-episode second season on May 23.