Ciao Leonardo,
Welcome to planDisney and thanks for stopping by with your question!
My family and I love the Pixar movies so - like you - it's a priority for us to try to meet as many of those
character experiences as we can on our trips to the Disneyland Resort.
Thankfully, they all typically hang out around the same spot:
Pixar Pier in Disney California Adventure Park! This makes them really easy to find though the days and times that they're around to meet Guests can vary.
However, there is a helpful trick within the
Disneyland Resort mobile app that will help you have a better sense of when you might be able to meet many of the characters that are out and about in the parks! While in the map feature of the app, you'll want to tap "Characters" from the menu of icons at the top of your screen. Next, I like to select the "Show List" button near the bottom right corner of the screen, which will show a scrollable list of all the characters who plan to stop by the parks in a given day. If you tap on a specific character then it will often show you times and locations you might be able to catch them throughout the day.
Thanks again for your question, Leonardo! I hope you have a wonderful next visit to the Disneyland Resort.
Have a Magical Day,
Greg