Despite the fact the world is full of actors, casting directors occasionally decide they can't be bothered to find new talent. It's the only way to explain all the folk who've played multiple parts on some of the most iconic shows in telly history.

Okay, maybe we're being cynical – perhaps the following actors were so great in their bit parts, they earned another shot at stardom within that show's universe.

Whatever the reason, the following performers all seem very familiar...

1 | Dean-Charles Chapman – Game Of Thrones

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Poor old Dean-Charles Chapman. Most people only have to die on Game Of Thrones once, but Chapman lost his life twice. He first kicked the wooden bucket as Martyn Lannister, via a Rickard Karstark strangulation, then as Tommen Baratheon, via grief and a window.

That must be a pretty conflicted call from your agent – "Good news, they like you so much, they want to work with you again! Bad news, they're assuming people won't remember you were already on the show. Also, they want to chuck you out of a window eventually. Happy birthday!"

2 | Karen Gillan – Doctor Who

So, Doctor Who fans know Peter Capaldi appeared in 'The Fires of Pompeii' (as a character named Caecilius) before he became the Doctor.

But did you know that Karen Gillan also appeared in 'The Fires Of Pompeii?' Long before she became Amy Pond, Gillan was The Soothsayer (who you can see in the slightly silly video above).

Interestingly, the Who team didn't bother to try to explain away this one, though Pond did have a canon affinity for Romans, so there's a vague connection.

3 | Michelle Williams – Baywatch

So these possibly aren't the most significant repeated appearances on our list, but we're too busy being astonished that future (multiple) Oscar nominee Williams was in Baywatch at all to care.

Williams played Bridget in 'Race Against Time' – above – then returned as 'Hobie's groupie' in (brace yourself for this) 'Second Time Around.'

'Second Time Around'?! It's almost as if the Baywatch writers knew that, one day, we'd be writing this list and deliberately titled that second episode in the name of coincidence.

We kind of wish they'd used their time machine for a more noble cause, but we'll take what we can get.

4 | Karl Urban – Xena: Warrior Princess

For many genre fans, Urban is Eomer from Lord Of The Rings, Bones from Star Trek, or Judge Dredd from, uh, Dredd. But for telly addicts, he will always be Cupid in Xena. Or Julius Caesar in Xena. Or a caveman in Xena. Or the evil brother of someone in Xena.

Yep, Urban was a mind-boggling FOUR separate characters on Xena, presumably because he's a super nice man and everyone wanted him around on set as much as possible. Also, they were filming in his native New Zealand, where there aren't so many actors to go round.

Still, it was worth the effort for Urban – it launched his career in a very specific way, as he explains in the video above.

5 | Brent Spiner – Friends

Be very, very careful when you read this entry, as there's a small chance it'll tear a hole in the space-time continuum.

That's because Star Trek's Brent Spiner didn't just appear as the guy interviewing Rachel for a job at Gucci in Friends, he also PLAYED HIMSELF ON JOEY (see above).

You have to assume that Joey exists in the same universe as Friends, mainly because Matt LeBlanc plays the same character in both. But does he? Because if Brent Spiner is a real person/actor in Joey, does that mean he was playing a role on Friends?

By that logic, Joey was an actor on Friends, so does that mean that Joey is a real person playing a role on Joey, as Joey, who is also an actor? If Brent Spiner and Joey are both actors on Joey, were they BOTH playing parts on Friends?

6 | Kali Rocha – Buffy The Vampire Slayer

Kali Rocha was originally cast on Buffy The Vampire Slayer as Cecily, one of Spike's key crushes during his pre-vamp years. It was a relatively minor role, certainly in terms of screentime, so the Slayer casting team probably felt safe when they recast Rocha as Halfrek, a vengeance demon.

They're weren't counting on eagle-eyed fans, who immediately leapt on the casting, using it to create fan fiction that filled the gaps between characters, theorising that Cecily was turned into the demon known as Halfrek.

Joss Whedon liked the fan theories so much that he made them canon, bringing Halfrek and Spike together and making Halfrek refer to him as William, his human name, to suggest they had already met when Halfrek was human.

However, because Rocha had originally been cast as two different characters, a handful of fans realised this retcon caused a bit of timey-wimey incongruity – Halfrek had previously announced her age, which meant that she would have already been a demon when Spike and Cecily met.

The matter was cleared up in Spike: Old Times, a one-shot Angel comic created solely to solve this convoluted casting conundrum (basically, Cecily was one of Halfrek's undercover identities, so she really was a demon when she first met Spike).

All this because some casting agent couldn't be bothered to find a different number in their Rolodex.

7 | Jack Cassidy – Columbo

No wonder Columbo could solve every crime put in front of him, he kept meeting the same murderers over and over again. Jack Cassidy didn't log the highest number of returns (Patrick McGoohan appeared in four episodes as four different murderers, Jack only managed three), but he was a major fan favourite, so we're going to focus on him.

Part of the reason he was so loved (hated?) was he played Columbo's first ever foe in 1971 (on TV – Columbo featured different baddies on the show's feature-length pilots, but Cassidy was the first proper murderer on the show itself) in 'Murder By The Book' (directed by a very young Steven Spielberg, trivia fans).

It's a mesmerising performance – layered, creepy, and infinitely punchable, Cassidy's Ken Franklin made a major impression. He returned to play Riley Greenleaf in 'Publish or Perish' in 1974 and The Great Santini in 'Now You See Him' in 1976, with each of his three contributions rated as all-time great villains.