Doctor Who is an all-consuming, unstoppable force that can just appear anywhere it likes, with little reason or context needed. It's almost like the Flux in Series 13, only, y'know, without the structure of the universe being torn to shreds.
We probably don't need to remind you that this show is bloody huge, and, as entertainment franchises go, bloody ancient. It's older than sci-fi stalwarts like Star Trek and Star Wars (and is only one year younger than Spider-Man), and it's spent the last 50-odd years spreading its Ood-like tendrils into some often unexpected places, away from the main series itself.
Other movies and TV shows, stage plays, comic-books, novels, random TV adverts, bizarre unofficial spinoffs, you name it: if it can be watched, read, played, or otherwise viewed with eyeballs, then Doctor Who's probably been in it at some point.
Several of these appearances were a lot more surprising than others though, so let's run through some of Doctor Who's most unexpected extracurricular cameos, from a Dalek chomping on a cigar, to the world's rarest packet of fish fingers...
10. In A Buffy The Vampire Slayer Comic-Book
Doctor Who and comic-books have a long and strange history, with the franchise jumping between numerous different publishers from the 1960s, to the present day.
As we'll discuss again later in this list, this has allowed the Doctor and friends to cross paths with some truly legendary comic-book characters, but few of these crossovers were as unexpected (or as completely and utterly random) as that time when the Doctor jumped over to the Buffy the Vampire Slayer universe.
A single panel in the 2007 Buffy comic No Future For You features two rather curious characters stood in front of a red telephone box. Though these characters aren't named, it's clear that they're supposed to be the Tenth Doctor and Rose, with the red phone booth serving as a copyright-safe nod to the Doctor's iconic blue TARDIS.
So what crazy adventure are they on here? Hunting down the Great Vampires? Hunting down the fish vampires? Well, considering that this single panel is all we get, we don't know, but if you're a fan of both franchises, it's cool to see nonetheless.