https://www.yahoo.com/movies/m/3cbf3a98-0a5b-3fe9-a365-a39d58760c24/ss_15-superheroes-everyone.html

For ten seasons from 2001 to 2011, Smallville documented a young Clark Kent’s growing pains as he learned to use his incredible powers. The show was a smash hit, charting Kent’s journey from high school in Smallville to life at the Daily Planet in Metropolis, and finishing just as he fully embraced his destiny and took on the role of Superman. Spanning more than 200 episodes, Smallville had a lot of stories to tell, and not all of them were about the future Superman. Fans of DC Comics were treated to appearances by a number of their favorite heroes and villains, many of them in their prototypical stages like Clark himself. From iconic members of the Justice League to heroes from the future and

15. Aquaman
14. Cyborg
13. Hawkman
12. Impulse
11. Black Canary (this was a terrible rendition of BC - did not do the character justice at ALL)
10. Zatanna
9. Stargirl
8. Dr. Fate
7. Martian Manhunter
6. Booster Gold
5. Blue Beetle
4. Legion of Superheroes (Cosmic Boy, Lightning Lad and Saturn Girl)
3. Brainiac5 (also from LOS)
2. The Wonder Twins (Zan and Jayna from Superfriends)
1. Superboy (Connor Kent)

I thought they were going to point out some lesser-known Easter-eggs or implied cameo appearances, but all of these were obvious to anyone that watched the show at all.