Rule of Three/Comic Triple:
Monty Python and the Holy Grail:
-"Who would cross the Bridge of Death must answer me these questions three, ere the other side he see....". >It is actually subverted four times; the first time, the three questions are all easy, so the knight easily crosses. The second knight unexpectedly receives a third, difficult question which results in his death, while the third knight unexpectedly gets an easy question again but fails to answer it correctly and dies. On the final set of questions, King Arthur subverts it again by asking a question back to the bridge keeper, resulting in the bridge keeper's death.
-Arthur, when deploying the Holy Hand Grenade shouts 'One...two...five!' Sir Galahad corrects him: 'Three, sire.' 'Three!'
-Additionally when reading a parody of the Bible: "...then thou shalt count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out."
Big Bang Theory:
-Sheldon knocks three times, then says 'Penny' or 'Penny and Leonard' and repeats the process three times. Unexpected: knock knock knock 'Penny!' knock knock knock 'Sheldon!'...