The team members were masters of disguise, able to impersonate someone connected to the target or sometimes even the target himself.
This was accomplished with realistic latex face masks and make-up. Some impersonations were done with the explicit cooperation of the one being impersonated. Also bona fides would be arranged to aid infiltrating the target organization. In some cases, the actor playing the IMF agent also portrayed the person to be impersonated (this most frequently occurred during Martin Landau's tenure on the series, beginning in the pilot) or the voice of the person being impersonated was dubbed. In other cases, a guest-starring actor would play the dual role of both the original and the imposter (Rollin, Paris, or Casey). Sometimes one or more IMF team members would allow themselves to be captured in order to gain more access to or knowledge of the organization they are infiltrating, either by conversing with the target or being held in a jail cell and hatching their plan there.
A few episodes of the early seasons showed the painstaking creation and application of these masks, usually by disguise and make-up expert Rollin Hand. This was later omitted as the series progressed and the audience presumably becoming familiar with the mechanics of the team's methods. In the 1980s revival, the mask-making process involved a digital camera and computer and was mostly automatic. Most episodes included a dramatic "reveal" (also referred to as the "peel-off") near the end of the episode in which the team member would remove the mask. A similar latex mask was used by Kurt Hendricks to fool Ethan Hunt and his IMF team that they were dealing with his second-in-command, whilst he made off with a briefcase containing Russian nuclear launch codes.