Danielle Panabaker (Kelsey) mentions that her favorite thing is snow. On The Flash, she plays Killer Frost, a super hero/villain with cold powers.
Danielle Panabaker makes a guest appearance in this episode. Kay Panabaker, Danielle's sister, also plays a patient in season 5 episode 10, "All by Myself".
Danielle Panabaker, the girl without a heart who loves the snow, stars as Dr. Caitlin Snow/Killer Frost on The Flash and the extended Arrowverse, which includes Supergirl, starring Chyler Leigh (Dr. Lexie Grey) as Dr. Alex Danvers, Supergirl's adopted sister; both play medical doctors, though more focused on the biology and study side of things than surgeons, and they've been in episodes together, though they've only shared a few scenes. They shared no scenes in this episode, though Panabaker shared all of her scenes with Leigh's real-life husband, who played her on-screen boyfriend.
Chyler Leigh and Nathan West also starred in 7th Heaven together. They were a couple.
Every episode of the show is named after a famous song. "Holidaze" is a song by Mansions.