Super Mario Odyssey is one giant celebration of everything coin and plumber related. A callback in the later portion of the game is a wonderful blast from the past.
Following the conclusion of Super Mario Odyssey, Mario ends up in the serene Mushroom Kingdom. In Odyssey, Mario is usually hunting down Power Moons, but the Mushroom Kingdom turns them into the Power Stars from Super Mario 64.
If players collect enough purple coins, which are the level's unique currency, they can purchase the kingdom's unique outfit, the Mario 64 suit. The suit transforms Mario into his blockier look from the Nintendo 64. Wearing that costume is the key to finding one of the kingdom's Power Stars, which involves a famous statue from Super Mario 64.
This is a picture from Super Mario Odyssey, not Mario 64.
The statue in question is the Eternal Star statue. Back during Super Mario 64's release, the statue was the focal point of an urban legend that claimed it was possible to unlock Luigi. Fans misread the statue's inscription as "L Is Real 2401," believing the L stood for Luigi. Over 20 years later, the statue holds a different secret in Odyssey:
Wearing the Mario 64 suit in Odyssey, players are able to enter a locked door that leads to the same courtyard where the statue was found in Super Mario 64. It features the same water fountain and dozens of low-fi 2D tree sprites.
If players toss Cappy on the statue in the fountain, they will find a Power Star. The achievement for collecting it is "Totally Classic!" If Luigi is in Super Mario Odyssey, I haven't found him. But at the very least, I finally got to collect the Eternal Star.