At around 16:35, Parker (Meaghan Rath) makes a reference to Taye Diggs in front of Jesse (Christopher Lowell). Previously, Christopher Lowell had worked regularly with Taye Diggs on the first Grey's Anatomy (2005) spinoff, Private Practice (2007).
When Ellen suggests sensory deprivation to Charlie, she mentions Busy Philipps' podcast. Busy Philipps played Rachel on S03E03 ("Third Wheel") of How I Met Your Mother (2005), which is in the same Universe as How I Met Your Father (2022)