If Doctor Who fans felt devastatingly old when 29-year-old Ncuti Gatwa was announced as the Fifteenth Doctor, things quickly got worse.
In November 2022, Millie Gibson was announced as the companion to Gatwa’s Doctor, joining him aboard the TARDIS in late 2023 as the new character Ruby Sunday.
Born in 2004, 18-year-old Gibson wasn’t even a year old when Doctor Who was rebooted in 2005. Still, it’s a sign of the show’s longevity that her casting came days before its 59th anniversary. It was also just a few weeks after The Power of the Doctor suggested that the Doctor’s real power was their wealth of companions. There were many familiar faces in the companion support group at the end of that special episode, including one of the Doctor’s first companions Ian Chesterton, played by the ever-young 98-year-old William Russell.
But as young as Gibson is, she’s not the first teenager to accompany the Time Lord on their adventures through time and space. The show’s classic era — when it stacked up 26 seasons between 1963 and 1989 — saw many actors join the show at the start of their careers, often becoming fan favorites.
When it comes to the youngest companions, things get a bit weird. Robot companions like Kamelion and several K9s weren’t very old when their last panel was soldered. Then, of course, there’s the awkwardness of the one-time companion and wife of the Doctor, River Song, who was conceived in the TARDIS.
We’ve put together the definitive list of the Doctor’s youngest companions, based on the age of actors when they started filming. That doesn’t often depart too far from their characters’ age, even if there have been a couple of school kids. Here’s the select group that Millie Gibson’s Ruby will soon join.
Turlough — Mark Strickson (21)
Schoolboy Turlough was played by 21-year-old Mark Strickson, who joined the show for its 20th anniversary season. Smartly dressed, wryly smart, and a traitor aboard the TARDIS for much of his debut episodes, he surpassed low expectations to become one of the Fifth Doctor’s most popular companions.
The use of his surname referenced his place at an English private school, but intriguingly, he was an alien exile. He wasn’t only the first male companion to join the show after Adric annoyed everyone, but the first red-headed companion too, and there hasn’t been a bad one since.
Amy Pond — Karen Gillan (21)
Perhaps the most famous redhead to step inside the TARDIS, Karen was a mere 21 when the Eleventh Doctor memorably crash-landed into her life, late and for a second time. She wasn’t the first TARDIS crewmember to hold a light for the Doctor — a distinctly modern Doctor Who development — but she was the first to jump the Time Lord on the eve of her wedding.
Amy would go on to be at the center of Doctor Who’s most timey-wimey storyline, marry the love of her life (after his resurrection as the Last Centurion), and give birth to a Time Lord hybrid (but don’t think too hard about that).
Peri — Nicola Bryant (21)
Californian botany major Peri replaced Turlough to become the show’s first regular American character (although Bryant is British). After the Fifth Doctor’s mixed bag of a TARDIS crew, his final companion stepped into some of the show’s greatest stories, including the Fifth Doctor’s bona fide classic finale, The Caves of Androzani.
Formally known as Perpugilliam Brown, she accompanied the Sixth Doctor for most of his tenure before making one of the show’s most surprising exits. Peri helped to define the modern template of a male Doctor and single female companion, reframing it from its mid-1970s heyday, ready for its triumphant 21st-century return.
Vicki — Maureen O’Brien (20)
Maureen O’Brien had one of Doctor Who’s most important jobs. Before Patrick Troughton’s Second Doctor proved the show could survive a change of lead, she showed it could survive a companion departure. In many ways, Vicki was a like-for-like replacement for Susan, the Doctor’s granddaughter and original companion (actress Carole Ann Ford had taken that role at 23).
Vicki was such a fill-in she didn’t even receive a surname, but she was an intriguing addition to the show. The short serial The Rescue introduced the 25th-century girl marooned on a hostile planet and later paired her with Peter Purves’ action man Steven, earning a place in TARDIS history in her own right.
Zoe — Wendy Padbury (20)
Futuristic Zoe was another of the Doctor’s prodigiously talented companions. She was a scientist who came from the far future of… Now. Yes, she beats Rose Tyler to be the Doctor’s first 21st-century companion, although the 1960s vision of the 21st century involved a much-advanced scientific education and jobs in space stations.
Zoe replaced Victorian Victoria to establish a brilliant trio with the Second Doctor and long-running companion Jamie McCrimmon. She’s perhaps most famous for her love of skin-hugging shiny one-pieces, which arguably made her the show’s first sex symbol.
Victoria – Deborah Watling (19)
Accompanying the Second Doctor, Victoria Waterfield joined the TARDIS in Victorian London and set a new bar as one of the show’s legendary ‘screamers.’ She was more than a good pair of lungs and became an enduring companion alongside 18th-century Highlander Jamie McCrimmon.
Only two complete serials featuring Victoria remain. We’re fortunate to have all of Tomb of the Cybermen and most of The Web of Fear, but her debut, Evil of the Daleks, is a significant loss.
Dodo — Jackie Lane (18)
There’s some confusion over Jackie Lane’s birth year, but a few sources cite 1947, making her 18 when she joined the TARDIS. Dodo replaced Vicki, becoming the show’s first wholly contemporary character for a few short months. Unlike her futuristic predecessors, Dodo was a bright and happy child of the 1960s, often seen in some undeniably groovy clothes and hats.
Unfortunately, she’s most notable for her abrupt departure (disappearing for a rest in the country), and that half of her serials are missing from the archive.
Nyssa — Sarah Sutton (18)
The 1980s was a peak for teenage recruits but also a mixed bag. One of the great successes was, unexpectedly, Sarah Sutton’s Nyssa.
Having had her sheltered life ripped apart by the Master, dressing in the ornate costumes of her Elizabethan homeworld of Traken, and hopelessly innocent bordering wet, the signs weren’t great. But the orphan became a firm favorite of Fifth Doctor Peter Davison and fans. It helped that she was crammed into a TARDIS with mouth-on-legs Tegan and less popular teen Adric…
Adric — Matthew Waterhouse (18)
Adric’s a problem. Undoubtedly one of the least-liked companions in the show’s history, he also suffered one of the show’s most shocking deaths. Don’t feel too bad — at least he had a cracking final line when he sacrificed himself to defeat the Cyberman in 1982’s Earthshock.
Stowing away aboard the Fourth Doctor’s TARDIS, Adric could have easily put the show off teenage companions forever. Fortunately, he and his Star of Mathematical Excellence didn’t. Matthew Waterhouse has subsequently joined Big Finish productions to help redeem the character on audio.
Ruby — Millie Gibson (18)
We’ll meet Ruby in late 2023 after the dust has settled on the 60th anniversary and Ncuti Gatwa’s Fifteenth Doctor has taken control of the TARDIS. She’ll become one of the show’s youngest companions, but as this list shows, the show has excellent form bringing teenagers to the show. She and Gatwa will form the most youthful combination of Doctor and companion since the 1980s — a real sign of intent for a new era.