“"Seinfeld" catchphrase ... or, when parsed as three words, how a participant of 17-, 30- or 47-Across might be greeted?”

Indian megacity of 16+ million

Talks too much

Text initialism that's the name of a 2010 Usher hit

Like some walls at Harvard and Dartmouth

"Casablanca" actor's nickname

Actress Long or Peeples

Native American rite of passage

Explosive item for Wile E. Coyote

"I wish it were so"