Crossroles

This series of interconnected Leverage crossovers started out as a simple Leverage / Supernatural story, based on Aldis Hodge having played both Alec Hardison and Jake Talley. It developed into a "5 times Alec Hardison met geeks from other TV shows" fic, and wound up as a 7-part, 28,000 word epic.

Title: Age(s) of the Geek.
Rating: varies from PG to R.
Genre: AU multi-crossover; gen, with hints of canonical pairings.
Fandoms: Leverage, plus Buffy, Veronica Mars, Doctor Who, Heroes and Supernatural.
Warnings: canonical character deaths, some angst, swearing.
Summary: When 14-year-old Alec Hardison meets 16-year-old Willow Rosenberg at a science fair, the friendship that develops will affect his future in unexpected ways.

Links:

You can find the full series at AO3 or read it chapter by chapter at LJ:

Chapter 1 (Buffy crossover)
Chapter 2 (Veronica Mars crossover)
Chapter 3 (Doctor Who crossover)
Chapter 4 (Heroes crossover, part 1)
Chapter 5 (Supernatural crossover, part 1)
Chapter 6 (Supernatural crossover, part 2)
Chapter 7 (Heroes crossover, part 2)