If the alternate reality episode (Episode 13: "If/Then") and the V-Day (Episode 14: "All You Need Is Love") weren't enough Big Event Episodes for you, don't worry: Next week we have a two hour Grey's Anatomy/Private Practice crossover extravaganza!

In this preview for Season 8, Episode 15: "Have You Seen Me Lately?" we see that Amelia (Caterina Scorsone), Derek's (Patrick Dempsey) troubled sister, comes to Seattle Grace-Mercy West to seek her bro's help with a difficult case.

Shepherd family drama is always fun, so we're looking forward to this crossover. Check out the preview here:

Credit: YouTube Photo: Grey's Anatomy Season 8, Episode 15 Preview: ''Have You Seen Me Lately?''

Grey’s Anatomy airs Thursdays at 9 pm ET/PT on ABC.

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