He appears disguised at the beginning of each episode with his own theme music to deliver Gadget his mission only to be blown up by the self-destructing message ( a parody of the Mission: Impossible messages ) because of Gadget's obliviousness ; he appears again at the end of most episodes to congratulate Gadget on a job well done, but he never realizes that it is Penny who is truly the one responsible for foiling Doctor Claw's plots.

The Doctor and Kari find the control room of Terminus and he realizes that Terminus is also a time ship.

When another Faust appears, everyone soon realizes that the Faust responsible for the kidnapping is actually a clone being manipulated by Doctor Hess.

During the fight with the Sinister Six, Spider-Man realizes that the Doctor Octopus, Electro, Rhino, and Sandman that they are fighting are robots while Mysterio and Chameleon are the only ones present.

He remembers Critas was wearing an out-of-period clasp with a red crystal, and Turlough tells him of Wrack's gift to Davey and the Doctor realizes the red crystals are the focus.

The Doctor, seeing the Buccaneer pull close, realizes that the focus must have been smuggled aboard somehow, and as he describes it, Tegan tells him about the crystal in the tiara.

As he is plummeting into the black hole the Doctor realizes his phone is still connected to the TARDIS and uses it to summon the TARDIS.

The Doctor realizes that the reason everyone has a sore throat is that they all have been emitting subsonic screams when under Shalka control.

The Doctor realizes that his surroundings are but an illusion and tries to deny their existence, but passes out from the strain.

Frank, upon hearing of Rachel's death realizes that Dracula is back and teams up with Blade, Hannibal King, and Doctor Strange to fight his return from the grave.

Only Rogue, Ms. Marvel, Beast, Falcon, Cyclops, Iron Man and Doctor Strange are left – they were the ones who were directly confronting Cap and Wanda – and a guilt-ridden Beast, learning from Uatu that Cap would have recovered from his illness and abandoned his manipulative relationship with the Witch as he became leader of a new team of Avengers if Beast had done nothing, realizes that he should have left everything alone.

The Doctor realizes the alien insect laid eggs inside the missing crewman, who became an alien now inhabiting the Ark.

Noah kills a crewmate, but recovers enough to order Vira to revive the remaining crew and evacuate, but the Doctor realizes the alien pupae will mature too quickly for this.

She realizes this over the course of her adventure with the Doctor and learns to feel hope again, placing it in the form of the Doctor, an alien who can literally come back to life, as well as regaining confidence in herself as a medical practitioner and as a person.

Finding Alex dead along with Doctor Morris Panov, Bourne realizes the trap as soon as he hears the police arriving.

The Doctor discovers that the playing card he was given by Valentine is a tracking device and it is calling the ' spirits ' to him and realizes that he must destroy it.

The Doctor realizes that he is stealing his victims consciousnesses and each card is tailored to its victim's touch which is why Valentine wears gloves when playing cards.

When Destrii realizes that Jodafra means to sacrifice Lakota children to the Windigo, she destroys the equipment that supports the Windigo, allowing the Doctor and the Lakota to defeat it.

The Doctor realizes he is cured since Leela's clone introduced into his blood stream her immunity factor.

While Rose goes with Pete to the wedding, The Doctor storms back to the TARDIS, only to find that it is now an empty shell, and thus realizes something is very wrong.

However, when Rose is taken away, the Doctor realizes his deadliest enemies have returned en masse.

While searching through his records, the Doctor realizes that Hex is actually Thomas Hector Schofield, Cassie's son, now a grown man.

In the end, the Doctor realizes they simply wanted him for his singing, not who he is as a sentient entity.

* in Doctor Who's first series after its revival, episodes 4-5 and 11 featured the alien Slitheen family of the planet Raxicoricofallapatorius, which were said to be Calcium-based life forms, causing them to be blown up in contact with vinegar.

The Slitheen family also reappeared in several episodes in The Sarah Jane Adventures series, as well as cameo appearances in later Doctor who Episodes.

In " World War Three ", when confronted by a group of Slitheen, the Doctor threatens to " triplicate the flammability " of a bottle of port wine with the sonic screwdriver, though one of the Slitheen realises he is bluffing.

In Doctor Who and the Sarah Jane Adventures, the Slitheen disguise themselves in human skin suits to infiltrate human society.

Also, in the new Doctor Who series, Blon de Slitheen survives the bombing of 10 Downing Street ( Series 1, Episode 5: " World War Three ") by teleportation to the Isle of Dogs ( Series 1, Episode 11: " Boom Town ").

The Autons returned in the 2010 episode, " The Pandorica Opens ", allying with the Atraxi, Blowfish, Chelonians, Daleks, Drahvin, Draconians, Sontarans, Cybermen, Haemogoth, Judoon, Slitheen, Silurians, Sycorax, Terileptils, Hoix, Roboforms, Uvodni, Zygons and Weevils to trap the Eleventh Doctor.

As the Doctor, Rose Tyler and their new friend Harriet Jones battle the murderous Slitheen while trapped in 10 Downing Street, the Doctor realises that the fate of the Earth rests on Rose's boyfriend, Mickey.

Following from the cliffhanger in " Aliens of London ", The Doctor being an alien allows him to survive the electrical pulse administered by the Slitheen Green, while Mickey Smith is able to push aside the police inspector who was advancing on Jackie Tyler.

The Doctor attempts to get the police, but by the time he has returned, the Slitheen have got back into their suits.

Before sealing off the rooms, the Doctor confronts the Slitheen and learns that they are a family rather than a race, and they are not invading Earth, but rather raiding it for some commercial purpose.

The Doctor gives Mickey instructions on how to log into the UNIT website on his computer, and uses that to determine that the Slitheen ship is presently in the North Sea, transmitting some signal that Mickey attempts to decode.

Complying, the Doctor helps Mickey to hack online into the controls of the Royal Navy HMS Taurean, a Trafalgar class submarine, to fire a non-nuclear missile at 10 Downing Street, where all the Slitheen conspirators are now gathered.

The museum's display items feature the arm of a Slitheen ( Raxacoricofallapatorian ) from " Aliens of London ", which Rose recognises, and something that the Doctor refers to as " An old friend, well, enemy ... " – a Cyberman head ( from Revenge of the Cybermen, but the label on its display case references The Invasion ).

In " Boom Town ", Mickey later meets up with the Doctor, Rose and new companion Captain Jack ( John Barrowman ) in Cardiff, where he helps them foil a Slitheen plot.

The Slitheen are a family of massive, bipedal extraterrestrials from the British science fiction television series Doctor Who and are adversaries of the Doctor.

Though the name " Slitheen " refers to a specific family, the term has been used by the Doctor and Rose to refer to the Raxacoricofallapatorian race in general.

Before the Slitheen could receive the launch codes, the Ninth Doctor arranged for a Harpoon missile to demolish 10 Downing Street, ending the scheme and killing all but one of them who managed to escape through an emergency teleport.

When the Ninth Doctor and Rose are arrested in the Justicia System in the year 2501, the Doctor shares a cell with Dram Fel-Fotch and Ecktosca Fel-Fotch Happen-Bar Slitheen, who claim that after the Earth incident, the remnants of the family went bankrupt and had become historians.

When the Doctor and Rose defeat an attempted Blathereen takeover of the system, the Slitheen are pleased to see they can once again become the profit-holders of their race.

Rose mentioned the Slitheen Parliament of Raxacoricofallapatorius in " The Christmas Invasion " ( though her impromptu speech was a pastiche of phrases she's picked up on her travels with the Doctor ).