When Randy motivates the gang to fight back and free the boat from the Flat Earthers, there is a lot of symbolism to a round Earth: they pick up the following objects in order: Randy picks up a small Globe, Myc picks up a statue of Galileo's bust, Gigi picks up a telescope and Brett picks up a larger Globe. Randy and Brett both picking up Globes of the Earth represents a "full circle" of the objects being picked up (the Globe also being round), Galileo is the one that proposed the Copernican Heliocentrism theory and is considered "the father of observational astronomy".
In reality, Kenny G mainly plays the Soprano Sax, but can also play the Tenor and Alto Saxophones, however, he plays the Tenor Sax at the wedding on the boat.
Kenny G plays the Tenor Sax, even though the note that Randy finds specifically says Tamiko requested that Kenny G plays the Soprano Sax at her wedding, not the Tenor Sax.
The coordinates lat. 5°12' long. 24°46' that Randy gives to the Flat Earthers is actually at the border between the Central African Republic and the Democratic Republic of Congo, right by Bangassou Issa.
The song playing when Tamiko walks down the isle is "Canon in D".