Jerry is suspicious when Rick brings a bum into the house and Rick refers to Jerry "having another day in Phil Collins' proverbial paradise". The 1989 hit song by Collins, 'Another Day In Paradise', addressed the way affluent people will ignore the plight of the homeless instead of helping them. It is possible the writers were subtextually comparing the accusations that Collins wrote the song as a hypocritical exploitation of the needy, with Rick's hypocritical self interest in the bum's health.
Like Jurassic Park (1993)'s Dr. John Hammond (Richard Attenborough), Dr. Bloom's cane is topped by a knob made of amber. Instead of prehistoric insects, Dr Bloom's cane displays a caricature of Charles Chaplin, specifically his hairstyle and eyebrows. The film Chaplin (1992) was directed by Richard Attenborough.
Disney Parks references: Pirates of the Caribbean, The Haunted Mansion, workers staying in costume at all times, It's a Small World, and Imagineers.
The appearance of Alexander is based on that of his voice actor - and friend of co-creator Dan Harmon - Rob Schrab.
Someone on the production crew pulled a microbiology in-joke. At the bone train station, critters which Dr. Bloom identifies as E. coli are actually closely patterned after Enterobacter phage lambda, a virus that infects E. coli.