Yemen Party - S3-E5
Other mistake: Donna tells Fatima (Cleveland in disguise) that she married Cleveland when she "was 41, with two kids." However, the first season established that Cleveland and Donna did not see each other for 25 years after high school. Donna was 43 when she married Cleveland.
Suggested correction: It's established she's 41 and there's too many assumptions to say she's 43. First, all she said was "25 years later and you're still giving me gruff about Robert". Meaning it's been 25 years since she started dating Robert and Cleveland didn't like it, not that it's been 25 years since they saw each other. However, not everyone graduates high school at 18. So even if we assume it's 25 years since graduation, we don't know how old she was when she graduated.