Science-y holes that let aliens into our own world are a staple of science-fiction TV, creating a reason for “monsters of the week” to appear semi-regularly and giving our heroes a cause to stay and fight together in one place. 

Examples from the past include the Hellmouth from Buffy the Vampire Slayer, the “anomalies” in Primeval and the rift in Torchwood – and now BBC America’s new Doctor Who spin-off Class joins the tradition by introducing “tears” in time and space that let creatures from around the universe enter the environs of Coal Hill School.

However, while the creators of the new sci-fi are happy to pay tribute to the trope – the first episode sees characters acknowledge their situation is similar to series like Buffy and Once Upon a Time – they do want to make one crucial distinction clear.

Despite what we ourselves have theorized, these “tears” are NOT the same thing as the “cracks” previously seen in parent series Doctor Who, which looked similar and also allowed creatures and energy to enter our world (as well as, you know, eating at existence).

The tear (top) and the crack (above)

“No, it’s a different thing,” Class and Who producer Derek Ritchie told RadioTimes.com on the set of the new series.

“These are 'tears' in time and space, and that was the crack. They’re gonna look different, gonna feel very different. It’s not the same thing at all.”

He added: “That crack was a very specific storyline, and represented a very specific thing. Whereas this is a much more general idea.”

Well, that’s us told. Then again, considering episode two sees characters refer to the phenomenon as “the bunghole of time”, you’d think calling it a “crack” wasn’t TOO far of a leap…

Class is currently airing on BBC America