On Jeffrey's office wall is a photo of Gilbert R. Hill who played Inspector Todd in the first three films (and who's character was killed in Superdetective en Hollywood III (1994)). Hill passed away in 2016.
When Bobby Abbott (Joseph Gordon-Levitt) goes over Axel's three other cases in Beverly Hills, he mentions that the third "wasn't his finest hour", which is referencing Superdetective en Hollywood III (1994), that Eddie Murphy despised and is the lowest rated of the series.
Talking about making the film to People magazine, Eddie Murphy said, "It was a hard one. I did Axel Foley when I was in my 20s. I am not in my 20s anymore. It was an action movie. So it was a rough one. But we got through it." For the record, Murphy was 23 when he did Superdetective en Hollywood (1984) and is now 63 in Axel F.