It's common for Pixar movies to be preceded by an animated short but with Coco, Disney tried something very different. Unfortunately, it doesn't appear to be working out very well. Coco is preceded by Olaf's Frozen Adventure an animated story that follows the living snowman from Disney's Frozen. However, while Frozen is one of Disney's biggest hits, Olaf's Frozen Adventure seems to be getting trashed by many of those same fans. People really seem to hate it.
First and foremost, it should be pointed out that calling Olaf's Frozen Adventure a "short" isn't strictly accurate. The film is over 20 minutes long. Disney technically referred to it as a "featurette," not that such a description gives anybody much indication what they're actually getting themselves into. The length seems to be the reason that a lot of people were unhappy with what they got prior to Coco. While people love Frozen, it doesn't appear anybody went to the theater to see Olaf.
It seems that originally the plan for Olaf's Frozen Adventure was for it to be a TV special on ABC, before somebody apparently decided that it was good enough for a theatrical release. Whatever the thought process there, it seems to be backfiring, as a lot of people have been tearing into the film on social media. While some might only be frustrated by how long it is, there are others who clearly feel that it's just plain bad.
On the plus side, negative word of mouth regarding Olaf's Frozen Adventure didn't harm the positive word of mouth that Coco itself has been receiving. The film recently earned itself an A+ Cinemascore and it inched out a box office victory over Justice League. Many of the same people who are being critical of Olaf online have nothing but good things to say about Coco, so it doesn't appear the bad experience dampened anybody's experience with the feature film. Some people are even able to have a sense of humor about the whole thing.
It seems that Frozen's hold on the people is not absolute, and Olaf's Frozen Adventure has found the limits. One certainly wonders if people will still remember this when Frozen 2 comes out in two years. Disney certainly wants to keep Frozen in people's hearts and minds as long as possible, though it seems right now people are ready to forget it.