Leto......ABC is introducing the spinoff in the old school way, by having the characters appear on an episode of the regular series.
This week's episode will be introducing the characters of the spinoff, so one half will focus more on Addison in, I believe, California, and the other half will be your usual Grey's stuff. Apparently, both Burke and Cristina's mothers are back for wedding planning, which should be good. I love Mrs. Rubenstein. So funny!