The police officer talking on the phone was presumably talking with Jesse Pinkman (referring to the caller as "sir") about the possum under his aunt's house.
The opening teaser is a flashback that establishes Kim Wexler went to "Red Cloud Jr. High School". This is most likely Red Cloud, Nebraska (named for a famous Oglala Sioux (Lakota) chief). An important clue to Kim's past growing up in the mid-west U.S. This reinforces details from past seasons, such as her owning a well-worn Kansas City Royals t-shirt she often wears to bed.
When Michael is looking over the coroners report for the Travelwire homicide, J.P Wynne is listed as the medical examiner. J.P Wynne is also the name of Walt's High School in Breaking Bad.
When talking with the two prostitutes, Howard mentions not knowing any "tugboat." In "How I Met Your Mother," Bob Odenkirk played a character obsessed with a dog of the same name.
When Kim returns home (near the end of the episode), Jimmy/Saul is playing guitar. The riff he is clumsily playing is "Smoke on the Water," a famous classic written by Ritchie Blackmore of Deep Purple.