It’s unclear exactly how David Tennant became the poster boy for the revamped era of Doctor Who, but like so many of the adventures of the centuries-old alien, it may be a matter of timing. His original run as the tenth incarnation of the Doctor came in the reboot’s second season, meaning the show had a whole 13 episodes under its belt to experiment with tone, structure, and mid-aughts-era BBC budgets (read: £3.17 per episode).

Within a few seconds of Christopher Eccleston (the underrated ninth Doctor) bursting into cosmic flame and replacing his physiology with Tennant’s in 2005 (Doctor Who cleverly figured out how to outlive its lead actors with the title character’s “regeneration”), the young Scot lit up the screen. It was as if he hadn’t just spontaneously combusted himself and instead merely cleared his throat.

Tennant led the charge for Who’s new legacy in the modern era, deploying his charm, cheer, and cheekbones with ruthless effectiveness. Over his four-year run, the tenth Doctor started to feel like the defining version of the character — his 135-minute finale was almost a weepy funeral for the actor, as if he were actually dying and not just considering other career options.

Now, Tennant is back — but in a different way to how he was back before. Anniversary specials in Who bring back former Doctors alongside the most modern incarnation (Tennant did it for the 50th!), but the latest, 14th version of the Doctor is an entirely new person who looks, sounds, and behaves just like Ten. For the first time, the Doctor has regenerated into someone he has already been (if we’re not counting the time Tennant literally already did that 15 years ago).

The 14th Doctor’s familiar face makes it clear that, for the 60th anniversary, newly reappointed showrunner Russell T. Davies wants to celebrate the brilliance of Tennant’s tenure as Ten. For the uninitiated or the simply nostalgic, here’s David Tennant’s ten most essential episodes.

“School Reunion” (Season 2, Episode 3)

It’s difficult to express how iconic this early Tennant episode is. The TARDIS team (here, Rose and Mickey) infiltrates a school where a race of shape-shifting bat creatures has replaced the teachers (led by a snarling, post-Buffy Anthony Head). But when the Doctor crosses paths with an old companion, Sarah Jane Smith (Elisabeth Sladen), sparks fly.

The cattiness and eventual warmth between Rose and Sarah Jane are delightful, but it’s a standout hour for Tennant: With Sladen, he has to convey a relationship explored by two separate ’70s actors, now buried in his own much older-younger character’s memory. There’s so much age in those fresh features — all the joy and heartbreak of coming in and out of human lives are on display.

“The Girl in the Fireplace” (Season 2, Episode 4)

Before he took over showrunning duties, Steven Moffat made guest-writer appearances during the RTD era, and his lone episodes remain true highlights. They run the gamut from funny to sad to utterly terrifying (“Blink” would be on this list if, well, Tennant was in it for more than five minutes). Moffat leaned into the intimidating side of the tenth Doctor’s confidence and intelligence, and he had less patience for people getting in his way.

“Girl in the Fireplace” tells a time-slipping tale between the French aristocracy and a futuristic spaceship in which Madame de Pompadour (Sophia Myles) is haunted by maniacal automatons (and a handsome Timelord) from the future. It’s lush, creepy, and weepy — early in his run, Tennant proved how ably he could be the dashing romantic. Having two hearts makes him a double heartthrob.

“The Impossible Planet” and “The Satan Pit” (Season 2, Episodes 8 and 9)

One of the finest “deep-space outpost” episodes of Who (industrial walkways! Control panels!), this two-parter mixes survival with spiritualism (and rips off a couple Alien films in the process) as the Doctor and Rose become marooned on a planet that’s positioned impossibly close to a nearby black hole. A crew member soon starts showing the symptoms of a man possessed, and the outpost’s docile alien slaves soon turn violent — just as the Doctor ventures deep underground to face the demonic presence haunting his new allies.

This Ten-and-Rose two-parter is crucial context for the season finale that would make them say good-bye, largely because they spend so much time apart. Something about their burning bond drives them to save each other even in the face of literal gods and monsters. Tennant musing about faith and the past while descending a pure black pit, not to mention his sacrificial face-off with an infamous demon, feels almost elemental — the behavior of a man who has survived everything pushed to his very limits.

“42” (Season 3, Episode 7)

It may seem odd to pick such a mid-tier episode to honor Tennant, but this survival story of a free-falling spaceship that’s exactly one episode’s run time away from colliding with an alien sun is the only Tennant episode written by Chris Chibnall, the Torchwood and Broadchurch writer who would later become Who’s showrunner during Jodie Whittaker’s run as the Doctor. (Tennant is the only Doctor to have been written by the three showrunners of the new era.)

Chibnall has Tennant’s intense, propulsive energy down to a tee; “42” proves how fun an unexceptional Who episode could be with Tennant at the helm. It’s got a ticking clock, a sun-infected slasher killer, and the Doctor almost becoming overwhelmed by a helioscopic god. Yes, this is considered unexceptional.

“Human Nature” and “The Family of Blood” (Season 3, Episodes 8 and 9)

Two-parters in Who were a great opportunity to give characters and story some more breathing room than was permitted within the rigorous structure of a 45-minute adventure. In this pre-WWI period tale, the Doctor escapes danger by disguising himself as a human — no, not just an assumed identity; he actually alters his alien biology to make it human. John Smith, a boy’s school teacher, is a normal man with normal human memories, and only the Doctor’s companion, Martha (Freema Agyeman), knows his real identity — or that he’s being hunted by a vampirelike alien family.

It’s one of the more affecting NuWho stories because it’s so human; we watch the Doctor form real relationships, living as an unassuming Englishman in a quiet part of the world, months before a world war changes the planet forever. Who are we to say that John Smith’s feelings and desires aren’t real, that he doesn’t deserve to be replaced as soon as the Doctor is needed? Tennant plays both the constructed and genuine sides to his character with a nuanced, subdued grace, leading us to a heartbreaking and almost gothic-styled ending.

“Utopia” (Season 3, Episode 11)

A game-changing episode in a standout season, the Doctor is reunited with swashbuckling time traveler Captain Jack Harkness (John Barrowman) on an almost barren planet at the end of the universe. There’s something so thorny about how the Doctor treats his former companion; Tennant and Barrowman bounce back and forth with a wary, knowing tension, exactly as two people cautious over each other’s superhuman abilities would be. If the Doctor feels like he’s lording over his advanced intelligence more than usual (Tennant’s Doctor was definitely one of the smugger ones), it’s probably because he’s trying to outdo Jack’s domineering energy.

But when the episode climaxes in a surprise reveal of the Master, the Doctor’s archnemesis he thought was dead, we see the Doctor like we’ve never seen him before. The terror, desperation, and utter powerlessness he’s confronted with upon learning that the worst possible person survived his race being wiped out gives such unearthly goose bumps. “Utopia” set up a barnstorming finale in which Tennant got to deliver loads more moments like these.

“The Unicorn and the Wasp” (Season 4, Episode 7)

Tennant’s last regular season paired the Doctor with the dynamic Donna Noble (Catherine Tate). They made for a hysterical odd couple with a pure love for adventure and each other’s company. This period romp threw the pair into a real-life Agatha Christie mystery with the real-life Agatha Christie (Fenella Woolgar) and a gigantic alien wasp. Tennant and Tate lean into their most farcical instincts with every suspect nailing the required campy delights of the genre. It may not be dramatically or cerebrally challenging, but it’s tough to imagine a more top-of-his-game Tennant.

“Midnight” (Season 4, Episode 10)

A clear candidate for Tennant’s best episode, largely because it’s hard to focus on anything except him. In order to combat budget constraints, some RTD-era episodes would feature very little of their main cast members; “Midnight” features barely any Donna, and in the next episode, “Turn Left,” the Doctor is present for only one or two scenes (these episodes were filmed concurrently).

But restrictions can force creativity: Even though “Midnight” takes place on primarily one set — a futuristic leisure bus taking tourists across an inhospitable diamond planet — it ranks as one of the most suffocating episodes of Who. An incorporeal entity somehow gets inside and infects a passenger. When she starts repeating everyone else’s speech, the passengers turn on the Doctor — pointing out all the understandably suspicious things about his arrival and interference — and seeing Tennant play the character constantly on the back foot is a subversive and tense delight.

When the entity infects the Doctor, his fascination with meeting a new type of life turns to paralyzing helplessness, and we face the terrifying prospect of our hero losing his life in the middle of nowhere at the hands of misguided nobodies. Tennant’s Doctor Who has never felt like more of a raw nerve, and Tennant’s Doctor has never been tested in a more distressing and intimate way. These humans he’d do anything to save certainly make it hard some days.

“The Waters of Mars” (2009 Special)

The ethics of time travel always felt more of interest to Moffat’s episodes, and if RTD did draw our attention to them, like in season one’s standout “Father’s Day,” the emphasis was always on the emotion of the story. Tennant’s penultimate adventure, the second of four specials that saw out his run, begins like a sterling but not groundbreaking space-outpost adventure — a water entity on Mars is attacking the first human colonists — before the Doctor realizes that the entire crew has to die if humanity’s future among the stars is to be fulfilled.

The final 20 minutes have Tennant, already playing a man contemplating his upcoming death, going full Vengeful-God Mode, transforming his planetary grief of losing his people into a righteous fury. He saves people who were fated to die because, being the last of his kind, he reckons the laws of time will have to bend to him rather than the other way around.

But in the final minutes, when he realizes just how recklessly far he went, we see the face of a man who has just been delivered an unholy sermon on intergalactic accountability — a sick inversion of the swaggering heroism that has defined Tennant’s era.

“The Day of the Doctor” (50th Anniversary Special)

It’s a long-observed Who tradition to bring back previous incarnations of the Doctor on anniversaries (since 1973!), and when the series turned 50 in 2013, Moffat paired Tennant up with Matt Smith and John Hurt, who played a previously unknown version of the Doctor from the Great Time War.

Writing for Tennant as a showrunner for the first time, Moffat softens the harder edges he used to give to the tenth Doctor, finding the happy balance of pathos and glee fit for an epic celebration. Tennant and Smith’s chemistry is unparalleled — the humor, insecurities, and swelling heroism of one only bolsters the other.

As he’s only a supporting character (this is, of course, Smith’s show now), we’re allowed the simple pleasure of enjoying his company with every frenetic gesture, clenched jaw, and overly stressed enunciation feeling like a warm hug. This is my No Way Home, or something.

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