The name of a Lego set in the Mixels line. Part of his description read: "Part
chicken, part frog, part back-of-the-bus window licker...", which seems
fine to people in the US, but over in the UK, window licker is a term for mentally disabled people. The name itself, however, comes from turgid, which means distended, which roughly matches his appearance both in the animated series and Lego set.
TL;DR:
Lego Mixel offends UK after being described as a window licker, slang for retarded in the UK.