Gus lists options to which he and Maximus could go for their "Big Boy Day." All of the options he lists are places he and Shawn went on previous cases. He mentions the planetarium (from Season One's "From the Earth to the Starbucks"), the aquarium (Season Three's "Six Feet Under the Sea"), Old Sonora Western Town (Season Four's "High Noon-ish"), Santa's Year-Round Village (Season Three's "Christmas Joy"), and the Yerden Estate Tour (Season Six's "Indiana Shawn and the Temple of the Kinda Crappy, Rusty Old Dagger").
When Shawn confronts Juliet about Lassiter and Marlowe in their kitchen he starts rambling acronyms, one of them being JTT, Jules mentions Jonathan Taylor Thomas is not an acronym. Maggie Lawson appeared on an episode of Home Improvement (1991): An Older Woman (1998) as the love interest of Brad, Zachery Ty Bryan, older brother of JTT's character Randy.
Gus says at one point that Rachael "went all Halle Berry in 'Boomerang' on a brother." Boomerang (1992) was directed by Reginald Hudlin, who also directed two episodes of Psych: Ferry Tale (2010) and True Grits (2012).
Woody asks everyone to take a closer look at the dead body, when they hesitate he says "there's nothing to be afraid of, its not like you're going to catch necrophylopigmentosis...probably." Necrophylopigmentosis is not a real word, it is a mashup of the words necrophilia (sexual attraction to dead bodies) and pigmentosa (a condition that affects sight). So Woody appears to be making a joke that they aren't going to become necrophiliacs just by looking at one, which he follows by mentioning that he doesn't know how to relate or talk to living women anymore.
Tritium is one of two naturally occurring isotopes of hydrogen, the other being deuterium; an isotope is when an element has extra neutrons in its nucleus. A hydrogen atom (protium) contains one proton and one electron, deuterium is made when a neutron is added to a protium atom; deuterium is a stable isotope, about 0.0153% of the hydrogen in sea water is deuterium, it is the only hydrogen isotope abundant enough in nature to be collectable. A tritium atom has two neutrons, however it is an unstable isotope and therefore radioactive, it has a half-life of 12 years and as it decays the extra neutron becomes charged and turns into a proton, thereby creating the isotope of helium-3. Tritium occurs in nature but only in very minuscule amounts, hence all industrially used tritium is man-made, specifically it is a waste product of nuclear reactors, which is why it is so expensive. Even though it comes from a nuclear reactor its radioactivity is very weak and poses little danger, unless it is ingested.