Animal Trivia: Unlike dolphins, porpoises are not very ----------?

Questions

Hitchhiker Guide: Words inscribed in large, letters on the cover of the Hitchhiker's Guide.?

Hitchhiker Guide: Vastly hyperintelligent pandimensional beings appear in our dimension as this.?

Potpourri: This writer wants her tombstone to read, "Big deal! I'm used to dust!"?

Potpourri: He made the brass fittings for "Old Ironsides".?

Potpourri: This mysterious explosion occured on June 20, 1908 at Tunguska?