Mr. Monk and the Genius - S7-E2
Character mistake: At the beginning when Monk is writing Natalie's check, we see a shot of it, but the I in "nine" isn't dotted. As meticulous as he is, Monk would never leave an I undotted (we've even seen him dot someone else's i) especially since it would bother him.
Answer: Notice also that in the opening credits scene when he is touching parking meters her also wipes his hand on his clothes each time he does it.