Based on the headcanon that John has a little voice recording from their mother that she sent to him not long before she died. She sent it to him because he was particularly disappointed to find he wasn’t chosen for a junior Nasa space programme when he was 10-years-old, and she died later that year.
Despite it having context, the message is very general and applies to most situations so John plays it all around Thunderbird 5 when he needs it the most, and transmits it down to Tracy Island because his brothers could definitely use it too. The message is particularly helpful on the boys’ sad days, days when they need a little reminder that their mother is always watching.
Today in the theater class I’m a student aide for, one boy asked my friend who moved here from England if he was an illegal immigrant. He responded, “Oh yeah, I just casually hopped the border between America and England you twat.”