Big Time Rush, the musical group featured in the Nickelodeon series “Big Time Rush,” will perform live at Universal Studios at 7 p.m. Saturday. Earlier in the day, there will be opportunities to see a not-yet-seen episode of the show that will be screened at the park’s Animal Actors Theater. Show times are 1 p.m. and 2 p.m. The concert is included in regular theme-park admission.