According to the mag, the "Grey's" stars enjoyed an afternoon at Katherine's Los Feliz home, where they were joined by such celebs as Kate Walsh, Sandra Oh and Rebecca Gayheart.
A source told People that Ellen, who is expecting a baby daughter in October with husband Chris Ivery, was "very excited to celebrate with her girlfriends."
"She looked gorgeous in a white summer dress with her hair in a braided up-do," the source added of the mom-to-be.
Reported gifts for the star included a Sleep Sheep toy mobile, Sleepy Safari stacking toys and organic towels and a swaddle wrap.
The sixth season of "Grey's" is set to launch on September 24 on ABC.
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