No, Steve Carell wasn’t there, nor were Sam Rockwell or Toni Collette or Amanda Peet or Maya Rudolph or Rob Corddry. But a few of the folks who helped work on “The Way Way Back,’’ which was filmed last summer in and around Marshfield, did show up at a screening at the Somerville Theatre as part of the Independent Film Festival Boston. (Also there was the movie’s locations assistant Sarahkate Sullivan, executive producer George Parra, set decorator Rena DeAngelo, and production designer Mark Ricker.) The comedy, co-written and co-directed by Manchester-by-the-Sea native Nat Faxon, is something of a love letter to Water Wizz, the popular water park in East Wareham which is the setting for several scenes. “The Way Way Back’’ comes out in July.