Evil Rick says that the laughing is just a noise the creature makes every 10 seconds. Between Rick's Neverland Ranch joke and his Mumford and Sons joke, which the creature laughs at both, exactly ten seconds pass.
When Rick and Morty first enter the Citadel of Ricks, a mutated Rick and Morty from the 'Cronenberg universe' (introduced in Rick Potion #9 (2014)) can be seen in the background.
When Morty sees a "Cowboy Rick and Morty", they are dressed similarly to Doc Brown and Marty McFly in Back to the Future Part III (1990), which was the original inspiration for Close Rick-counters of the Rick Kind (2014).
One of the Morties looks just like Eric Stoltz from Mask (1985). This is an in-joke to the fact that Rick and Morty are based on Doc and Marty from Back to the Future (1985); Marty was briefly played by Eric Stolz before he was replaced by Michael J. Fox.
At 16:05 Morty is handed a pamphlet called "The Good Morty" by evangelical alternate Morties. The pamphlet is based on so-called "Chick tracts"; short, evangelical gospel tracts created and published by American publisher and religious cartoonist Jack Chick (1924-2016). A copy of the Good Morty pamphlet was included with the Blu ray for this season.