"The Slayer Collection" was a British invention that put together a series of four episodes for each of the major characters on "Buffy the Vampire Slayer." Of course, fans of the show already have all seven seasons on DVD so we hardly need to pick up any of these specialty discs, but there is still the academic question of whether or not they did an adequate job of selecting the right four episodes for "Buffy the Vampire Slayer, The Slayer Collection: Giles."
"The Dark Age" is an early second season episode that starts off with a demon that possesses bodies coming to Sunnydale as it tracks down anyone representing a particular Etruscan tattoo. The latest corpse turns out to be someone from Giles' past and the tattoo is revealed to be the Mark of Eyghon, a demon that Giles and Ethan Rayne worshipped when they were young punks. Now Eyghon is making the rounds killing everybody in the old gang and Giles and Ethan are last on the list. Then, just to make things interesting, Eyghon takes over Jenny's body. If you think this causes problems for her relationship with Giles, then wait for the next episode on this DVD.
"Passion" from later on in the second season is probably my favorite Giles episode containing three memorable moments. The first is when Giles discovers that Angelus has killed Jenny Calendar and left her in his bed, the second is when Giles launches an assault on Angelus at the warehouse, and the third is when Buffy knocks some sense into her Watcher and tells him that she cannot do this without him.
"A New Man" from Season 4 is when Ethan Rayne returns to Sunnydale, talks Giles into going out for a beer, and turns the former Watcher into a Fyarl demon. Those are the ones that are very strong and have a paralyzing hard-as-rock mucous (but no sizzling eye beams). Unfortunately Buffy things that this particular Fyarl demon has done something to Giles so she is hunting him down and Giles has to turn to Spike, who happens to speak Fyarl, for help.
"Lies My Parents Told Me" comes from the show's final season and to my way of thinking is more of a Spike episode. Giles returns to Sunnydale with news that he found a way of removing the trigger that causes Spike to do bad things. While Spike flashes back to 1880, just before Drusilla turned him into a vampire, Principal Wood reveals to Giles that his mother Nikki was one of the Slayers killed by Spike. Giles tries to keep Buffy diverted while Wood goes after Spike, but she catches on and ends up turning her back on Giles, so it has some minor importance but not enough to be in the top four for Giles.
That last one is the obvious one to replace in this quartet and I would think that "Helpless" from Season Four (a.k.a. "Giles Gets Fired") is the obvious one to substitute here to most easily justifying bumping the rating up to a legitimate five stars. I think they made a conscious decision not just do all Ethan and Giles episodes, because having "Halloween," where we first learn about Giles good old Ripper days, and "Band Candy," where Giles goes back to being Ripper, could make sense here as well. Giles goes back to England for most of the last couple of seasons so the pickings are rather slim there and his surprise appearance at the end of "Two to Go" is a great moment but the one line hardly constitutes a "Giles" episode.