It was Night on Monday's — which proved to be exactly what the show needed to see the season's first perfect score.JoJo Siwa and Jenna Johnson hit the stage late in the episode, where they delivered a foxtrot set to «Look at Me, I'm Sandra Dee (Reprise)» from the 1978 classic musical.Siwa — portraying Frenchie — and Johnson, as Sandy, donned pink ensembles for the emotionally stunning routine, and their performance left the judges in awe.Judge Len Goodman actually stood to deliver his feedback,