The character of Ellie is played by former U.S. Olympic gymnast McKayla Maroney. Maroney was on the 2012 Summer Olympic team where she won a gold medal in the team and an individual silver medal in the vault event.
When Brennan and Arastoo take a second look at the bones you see two images on the screen in the bone room. Those images are from season 3 as the teeth marks from Gormogon and his Master.
Rachel Howes is played by Cherami Leigh, who is an Anime and Video Game voice actor, best know for playing Lucy in Fairy Tail, Asuna in Sword Art Online, and Makoto in Persona 5.
When they goto "lake Anna" to retrieve the body they are surrounded by hills. Hills like those are no where near lake Anna.
Cam and Aristoo debate her anger over the identity thief, and whether she should or shouldn't "let it go", with particular stress on that phrase. This episode was transmitted just two weeks after the opening of Frozen.