In "Something Blue", a spell by Willow goes awry, blinding Giles, making Xander a literal demon magnet, and causing Buffy and Spike to fall in love and get engaged.
Going to Oz's place, Willow finds it emptied and realizes he has had his possessions forwarded to him without getting in touch with her, crushing her last hopes of his return.
When Giles drops by and asks why she did not show to help him perform the truth spell as scheduled, she admits feeling pressured to live up to high standards so soon after her break-up with Oz.
Xander continues to try to console Willow, but in an act of misdirected rage and grief, she calls him a "demon magnet".
While Buffy and Spike cuddle and kiss and make plans for the wedding, Giles calls Willow for help, confessing that he is totally blind.
In the meantime, Willow politely turns down D'Hoffryn's offer and he sends her back; giving her a talisman she can use to summon him in case she ever changes her mind.
Vox, ranking it at #19 of all 144 episodes on their "Worst to Best" list, writes, "The hilarious 'Something Blue' takes Willow's misery over Oz leaving and turns it into some bonkers 'what if?'
Willow's attempts to heal her broken heart with magic go horribly awry when her spell instead compels everyone to take her literally, making Xander an actual demon magnet and Buffy and Spike a happily engaged couple prone to sloppy public makeouts.
Club called it "a well-balanced episode", mixing comedy with more serious reflection on the theme of how there's no easy solution to Willow's problems.