Mayhem is a Spark that appears in Mario + Rabbids Sparks of Hope, specifically in The Last Spark Hunter DLC. Mayhem is found in the Melodic Gardens, from the Spark Quest Treasure Hunter, where it is confused about a pirate map. After the quest is complete, Mayhem joins the heroes.

Mayhem is an orange Spark wearing purple and green swirly glasses covering its eyes. It is the only Spark to wear glasses.

Source: https://www.mariowiki.com/Mayhem