The only way to really develop OCD quickly is to acquire it because of PANDAS (see the previous two questions and answers). Otherwise, OCD tends to develop gradually over the course of months or years. However, certain traumatic events may quicken the development of OCD. For example, if a person is worried about being fired and therefore attempts to do everything perfectly, but he gets fired anyway because of cutbacks and not because of anything related to his performance, he may still blame himself for not being perfect enough. This could increase the symptoms of his OCD, and his perfectionism could jump out of control.
Often, individuals attempt to hide their OCD until it is very difficult to fight and becomes apparent to others. This is unfortunate, as early therapy can be very helpful. Once others notice the symptoms, it may appear as if there was a rapid onset, but the sufferer may have just been hiding or masking her OCD for years.