In "Mr. Monk and Little Monk," in a flashback to 1972, the 5-dollar bill held up by the school principal is an old bill appropriate to the era, at least in the full shot. Unfortunately, in the close-up/insert, it's a *new* bill, not issued until the 90s, with Lincoln's head much larger on the face. The principal's signature on the bill also moves, from the lower corner on the old bill to the upper corner on the new/wrong one.