"Brand New Day" is a song from the musical "Dr. Horrible's Sing-Along Blog," not performed by Neil Patrick Harris but by Felicia Day, who played Penny in the production. Neil Patrick Harris, on the other hand, played the lead character, Dr. Horrible (Billy), in this online musical.
The musical was created by Joss Whedon and his brothers, and it gained popularity for its unique format, being released online in three acts during 2008. Neil Patrick Harris showcased his singing and acting skills in the role, contributing to the success and cult following of "Dr. Horrible's Sing-Along Blog." While he might not have performed "Brand New Day," his involvement in the project is noteworthy.