Here's a look at tonight's sci-fi TV:
Chuck, "Chuck vs. the Nacho Sampler" – Kristin Kreuk's Hannah sends the dateless Nerd Herd workers into a panic during her first day at the Buy More. Chuck struggles to recruit a new agent, and Shaw teams up with Sarah (who, by the way, looks great wearing tight and geeky Battlestar gear) for a secret mission. Elsewhere, Awesome is forced to deflect Ellie and Morgan's suspicions about Chuck's double life. It sounds like this one's packed with plot. I'm looking forward to seeing Kreuk interact with Morgan and the rest of Chuck's mutant friends. She's much more adorable here than she ever was on Smallville. (8 p.m. ET on NBC)
Heroes, "The Wall" – Samuel goes full-on bad guy as Claire and Lauren attempt to spring HRG from the carnival. Peter visits Sylar's own personal Oz to help him battle his worst nightmare. There's only one more episode left, and I really, really hope it doesn't involve a killer cello!
Head after the jump for clips and more TV picks.