Saturday's Seattle International Film Festival highlights:

"Earthbound": This is-it-or-isn't-it-science-fiction comedy set in Dublin has a vibe similar to "Blast from the Past" and features a winning, uncannily persuasive performance by Rafe Spall as a twenty-something geek who's convinced he's an outer-space alien trapped in exile on Earth. Needless to say, his secret makes romance (with a consternated Jenn Murray) and steady employment difficult for him. Light fare — but nicely shot and performed with exquisite comic timing and heart. It's having its world premiere at SIFF. 9:30 p.m. Saturday at Pacific Place; also screening 2 p.m. Sunday at SIFF Cinema Uptown and 6:30 p.m. Thursday at Pacific Place. Director Alan Brennan is scheduled to attend the Saturday and Sunday screenings.

Michael Upchurch, Seattle Times arts writer

"The Substance: Albert Hofmann's LSD": AMC's current "Mad Men" and a recent issue of The New York Times' Sunday magazine suggest that it's time for LSD to be reconsidered. So does this provocative Swiss documentary, which focuses on the drug's creator, Albert Hofmann, who was 102 when he died in 2008. The writer-director, Martin Witz, makes persuasive use of an extensive and reflective interview with Hofmann, who introduced the world to LSD in 1943. While Hofmann deals with his hopes and fears about the drug (his "problem child"), Witz tries to create an evenhanded history that touches on the spiritual nature of some experiences. Bizarrely, Ronald Reagan and Art Linkletter are shown advising to "just say no" — surprise — while the endorsements of Cary Grant and Aldous Huxley are ignored. 9 p.m. Saturday at SIFF Cinema at the Uptown; also screening 4:30 p.m. Wednesday at the Uptown.

John Hartl,

Special to The Seattle Times

"The Standbys": This charming and surprisingly moving theater documentary by Stephanie Riggs profiles three Broadway actors you've probably never heard of — because they've spent much of their careers as understudies and standbys for bigger-named stars. "Most actors would rather die than have their understudy go on," notes a theater veteran in the film; and indeed, Ben, Merwin and Aléna sit and wait, dreaming of their moment and pondering for Riggs' camera the oddness of having a Broadway performing career that often doesn't involve actual performing. By the end, we're rooting for all three to get their time in the footlights; all are, as we come to know them, clearly meant to be stars. Watch for a quick appearance from former Seattleite Cheyenne Jackson. 5:30 p.m. at SIFF Cinema at the Uptown; also screening at 4 p.m. Monday at the Harvard Exit. Riggs is scheduled to attend the first screening.

Moira Macdonald,

Seattle Times movie critic