Season 6, Episode 11: "The Switch"

-Hi, Cosmo. -Hi, Mr. Clotworthy.

-How are you today? -Couldn't be better.

-Hi, Lorraine. -Hi, Cosmo.

-My mom, Babs. -Hi, Mrs. Kramer.

-Lorraine. -Yes, it's a fine day.

-What do you say, Cosmo? -Hey, everything, my man.

-What? -I don't know the exact pronunciation...

...but I believe it's "ménage à trois."