Fans of Yehuda Fine ("Elders React to the Scary Elevator Prank") point out that his unusually stable disposition while discussing how he'd react and retaliate if he was in such a position was actually quite horrifying. Did any of them stop to realize that Benny and Rafi grew up with this guy?
A case of this would probably be Athena Stamakinley's departure from Kids React. Fans know her as the girl with the stuffed koala. After she made an appearance at the Daytime Emmy Awards at age 14 with the Fine Brothers and the other Kids React regulars, rather than graduating to Teens React upon entering high school like Lia, she just disappeared from the series altogether. Why? Probably because that, as a high school freshman now, she would have to stop taking her precious koala with her to React recordings or else that her peers, after seeing any possible Teens React episodes with her on the panel, would mock her for being too childish for her age. Aw, poor girl.
It was totally absent during her arc in My Music, but the difference there is that she acted in that series, so of course she wouldn't have her koala there. It's likely that she brought it for only Kids React recordings, where she could be more like herself.
During "Teens React to Slender", Lia notes that "it's thundering!" which (IIRC) only happens after a page is collected; however, she gets caught without finding any pages at all.
It MIGHT be that it's just noisy outside. We'd probably have heard it though.
In "Teens React to Royals by Lorde", Tom waxes over Lorde for a bit, then laughs awkwardly at his own words as he mentions that his girlfriend is in the waiting room. Oh, like the fact that this is going on the Internet would be any less damaging?