Producer Chuck Lorre ends each episode with what he calls a "vanity card" - At the top of the screen you see "Chuck Lorre Productions" and a different number followed by a big paragraph of quirky remarks. The card appears onscreen for less than 2 seconds, not enough time to read it. Each episode has a different card.
The end of the opening montage for the series has several pairings of word expressing opposites, such as: sun and moon, yin and yang, sugar and spice.