Philip's disguises is part of Philip (and Elizabeth's) spy craft to preserve their American identities. He used over 50 disguises during the series. Philip's most used disguise is "Clark Herbert Westerfeld", from the Office of Professional Responsibility (OPR), the office that oversees all federal intelligence agencies. Clark maintains his unwitting agent Martha Hanson who is secretary to the FBI's Counter Intelligence director. Where names are not provided for his disguises, a moniker or description is given. Its first appearance is in the Season One episode "Pilot".
After Errol Bengoster leers over Paige at the mall, Philip dresses as a blue-collar worker. He surprises Errol barbecuing in his back yard, beats him up and stabs him several times with a BBQ fork. He then warns him to stay away from underage girls. Matthew Rhys has referred to this persona in several interviews as "Fernando."
In order to blackmail Viola Johnson into putting a bugged clock into the study of Secretary of Defence Caspar Weinberger, Elizabeth poisons Viola's son. Later, Philip has to fight Viola's brother and smother Viola's son with a pillow in order to get her to co-operate.
After causing an accident involving an FBI car with a communication encryption unit in the trunk, Philip poses as a man needing a car repair so Elizabeth can sneak into the FBI car's trunk and steal the encryption code.
In order to revoke an assassination contract the KGB gave to a West German killer, Philip and Elizabeth question an arms dealer the assassin met with. The arms dealer's daughter Lana pulls a shotgun on Elizabeth and Philip disarms her.
After spending the evening with Martha, Clark is confronted by Agent Chris Amador and stabs him in self-defense. He spends the rest of the episode in the Clark disguise while treating Amador's wound and trying to get information from him.
Posing as an American agent, Philip meets Matteen and Salar in an Afghan restaurant. Intending to leave Matteen alive to warn Afghans to not collaborate with the US, Philip has to kill them both and then kill a busboy who witnesses him leaving.
In a sting operation with fellow Illegal Emmett Connors, Elizabeth and Emmett's wife Leanne have sex with Lockheed employee Roy Oatway until Philip and Emmett "catch" him in the act and posing as Air Force security, tell Roy they'll be giving him new security codes.
Posing as CIA Security agents, Philip and Elizabeth question Captain Andrew Larrick to determine whether he killed the Connors. Later, he uses the disguise and comes upon Larrick having sex outside a gay club.
While posing as Clark's sister "Jennifer", Elizabeth learns that Philip's Clark persona is an animal in bed. Curious, she surprises Philip at Clark's apartment, telling him she wants to experience sex with him as Clark. However, she comes to regret it.
Dressed as a janitor, Philip gains entry to the computer room. After attaching a computer to the ARPANET to download its information, he has to kill a student who returns to the room to get his wallet. Matthew Rhys has referred to this persona in several interviews as "Fernando." He previously wore this disguise in the Pilot.
Martha tells Clark that she doesn't feel right continuing to bug Agent Gaad's office anymore. Later, he visits Martha, planning to play a doctored recording of Gaad insulting her, but doesn't have the heart to play it.
Posing as Rendell's backup driver, Tom Braidic, Philip shows a fake driver's license to a security guard who lets him in the Contra training camp. A goof exists on the license as it says that his sex is female.
Dressed in the same disguise he convinced Fred to work for him in "Cardinal", Philip meets Fred and warns him that the FBI are conducting interviews with everyone who was at Stealth program conference.
Posing as Swedish intelligence agent Scott Birkeland, Philip convinces Annelise to get herself invited to a party for Pakistani intelligence members and talk to Yousaf Rana. Philip previously handled Annelise in The Clock but without a disguise.
Philip meets Fred who relates that he's found an unnamed $100M line item in Lockheed's budget which he believes is for the Stealth aircraft program. Fred tells Philip that John Skeevers may have details on Stealth.
Posing as a Vietnam war vet who fought at Hamburger Hill, Philip meets an ex-employee of Lockheed, John Skeevers, whose work with stealth aircraft paint gave him cancer. Philip learns details of the paint from Skeevers after giving him money.
Frustrated with no one paying attention to her concerns over staff leaving files on the Mail Robot, Martha takes numerous files and brings them home for Clark. She also reveals she knows he wears a toupee.
Philip receives a call from Fred that he was successful in getting a stealth aircraft paint sample but that he's been shot. Later listening to a police scanner, Philip and Elizabeth learn that Fred died of his wounds.
Philip continues to handle his agent Annelise to obtain information from Yousaf Rana, however, she falls in love with him and reveals her role for the KGB. Yousaf strangles her and seeing an opportunity to blackmail him, Philip promises to make Annelise disappear.
With Yousaf's help, Philip breaks Annelise's arms and legs and stuffs her into a suitcase while Elizabeth photographs. Later, Philip meets Yousaf and asks for the names of those working in the CIA's Afghan group.
In order to bug CIA Afghan group director Isaac Breland's briefcase, Philip poses as lawyer and lobbyist James. He befriends Isaac's 14 year old daughter Kimmy by getting fake IDs for her and her friends and smoking pot with Kimmy.
Posing as a consultant who helps defense contractors bid on projects, "Jack" takes his smitten girlfriend "Michelle" out for dinner with Northrup employee Lisa to convince her to provide information for money.
After a fight with Elizabeth, Philip visits Martha unexpectedly, not knowing that the bug in Agent Gaad's office was discovered. She demands to see his apartment, which he complies with, but she's still suspicious of who he really is.
After the bugged pen is found in Agent Gaad's office and Walter Taffet from OPR investigates, Martha realizes that Clark isn't from OPR. Philip has to convince Martha that he loves her and will do anything to protect her in order to settle her down.
Taking a chance that Mertha has told the FBI about him, Clark arrives at Martha's to find her happily cooking and not worried about his identity. A call from child services results in her putting off adoption and she continues to tell him about activities in the office, including that the Mail Robot has been sent out for repairs.
Wearing his Birkeland disguise, Philip and Elizabeth stake out a hotel lobby to determine who the hotel manager is. After finding it's a man, Elizabeth seduces him in order to get information on which rooms three Afghan Mujahideen will be staying in.
With Elizabeth, Philip is disguised as a CIA Agent and meet with Abassin Zadran who they manipulate into killing the other two Majahideen commanders. Philip previously wore this disguise when posing as Air Force security. ("Comrades")
Posing as "Patty's" brother, John blackmails Don Seong into paying for her fake funeral expenses, leaving Gabriel and a KGB computer expert alone in his office where they steal the codes to get William access to restricted pathogens.
Investigating whether the CIA is testing various insects to destroy Soviet grain crops, Philip and Elizabeth dress as cowboys and break into a laboratory in Oklahoma. Surprised by the lab's deputy director Randy Chilton, they question him and Philip snaps his neck.
Tailing Evgheniya Morozova, Philip and Elizabeth later discover she's having an affair with one of her students, a CIA agent who'll be posted to Moscow. Elizabeth photographs her and the agent for a blackmail plot.
With Gabriel having returned to Russia, Father Andrei, contacts Philip to pass on some intelligence. However, Philip tells him that Gabriel's replacement will arrive in a few months and he can't meet with him regularly.
Assigned to identify and kill WW2 Soviet war criminal Anna Mikhaylovna Prokopchuk, Elizabeth and Philip hear her harrowing story. However, Elizabeth still kills Anna and her innocent American husband, John Granholm.
In order to help Elizabeth with a blackmail plot, "James" visits Kimmy in Ann Arbor and convinces her to meet him in Greece by having sex with her. Later, he calls her, tells her he can't see her again and warns her to not go to a Communist country while in Greece.
Meeting Father Andrei, Philip learns that Father Viktor was questioned by the FBI and that he suspects Viktor told the FBI about Andrei working with the KGB. Realizing they are being watched, Philip flees and narrowly avoids capture by two FBI agents.
Using a Canadian passport, Philip is checked by the US border patrol and passes despite the patrol having sketches of several of his aliases including the one he wore when trying to exfilrate "Harvest" and "Clark." The name on the passport is difficult to read but it indicates his persona resides in Ontario.