Walden mentions that his 'dream woman' would be Mila Kunis. Ashton Kutcher (Walden) and Mila Kunis were co-stars in 'That 70s Show', are now engaged to be married and have recently welcomed their daughter to the world.
For Halloween, Alan (Jon Cryer) dresses as Duckie from Pretty in Pink (1986), a character who was played by Cryer.
The doctor mistakes Alan's costume as Ferris Bueller, likely a reference to how Jon Cryer and Matthew Broderick, who played Ferris Bueller, often get confused.