Sure.
1. 100: Voltorb, 200: Misdreavus, 300: Skitty, 400: Bibarel.
2. Body Slam by a longshot.
3. Follow Me comes third, after Helping Hand and Snatch.
4. TM 50 is Nightmare.
5. Arcanine, Suicune, Slaking. Spencer was a Frontier Brain in Emerald.
6. Six: Dratini, Dragonair, Dragonite, Gyarados, Aerodactyl, Snorlax. When Hyper Beam was actually viable.
7. Only four had 130 attack: Machamp, Kingler, Rhydon, Flareon.
8. Attract, Stomp, Rollout, Milk Drink. TREMBLE!
9. Meteor Mash is called Comet Punch, Sheer Cold is Absolute Zero, and Last Resort is Treasure.
10. You stood in the center of the room and used Fly to unlock Registeel's lair.
11. 252 EVs + 31 IVs + Nature + lv50 = 200.
12. Occa Berry reduces Fire damage.
13. The magnets can all learn Explosion now.
14. Four: Spike Cannon, Zap Cannon, Hydro Cannon, Flash Cannon.
15. I screwed my wording on this and forgot to edit it. I should have said evolutionary lines or final forms and not Pokemon. Regardless, they're Bronzong, Magnezone, and Forretress.
16. Six: Air Lock, Clear Body, Shell Armor, Pure Power, Insomnia, and Solid Rock. Nothing else does EXACTLY the same thing as another, so Shadow Tag and Arena Trap aren't correct.
17. Venusaur learned Petal Dance for the first time in G/S/C as an egg move.
18. Double-Edge is Blissey's last.
19. A Rocket Executive uses a Houndoom against you during the radio tower takeover.
20. Twelve: Sunkern, Tyrogue, Spinda, Snorunt, Glalie, Castform, Mew, Celebi, Jirachi, Manaphy, Phione, and Arceus.
There we have it!