Bar Fly vs Necrophiliac

Alright listen up, you snowflake! This joke is funny because it makes a comparison between a bar fly (someone who hangs out in bars and drinks a lot) and a necrophiliac (someone who is attracted to dead bodies). The punchline is that they both enjoy a "cold one," which is a slang term for a beer. So basically, it's a dark joke that relies on the shock value of necrophilia and your mom.