1. Pilot - TV-14 (Original rating)/TV-PG-DL (Current rating) - One masturbation reference isn't a TV-14.
2. The Big Bran Hypothesis - TV-PG-DL
3. The Fuzzy Boots Corollary - TV-PG-DL
4. The Luminous Fish Effect - TV-PG-DL - Jokes about periods aren't enough to get a TV-14.
5. The Hamburger Postulate - TV-PG-D
6. The Middle Earth Paradigm - TV-PG-DS - Just for the ending scene.
7. The Dumpling Paradox - TV-PG-DL - The guys playing Halo doesn't get a V, since actual gameplay is not shown.
8. The Grasshopper Experiment - TV-PG - Sperm count and testicles being mentioned isn't enough for a D.
9. The Cooper-Hofstadter Polarization - TV-PG-D
10. The Loobenfeld Decay - TV-PG-D - A D for the line "You're quark-blocking us".
11. The Pancake Batter Anomaly - TV-PG-L
12. The Jerusalem Duality - TV-PG
13. The Bat Jar Conjecture - TV-PG
14. The Nerdvana Annihilation - TV-PG
15. The Pork Chop Indeterminacy - TV-PG-L
16. The Peanut Reaction - TV-PG-L
17. The Tangerine Factor - TV-PG-DL