VGFacts

Every now and then, a notification will pop up saying, "Thank you Sonic! But the chaos emeralds are in another zone!". This is a callback to the original Super Mario Bros. where upon completing one of Bowser's castles, Toad says the infamous line of "Thank you Mario! But the Princess is in another castle!"

Another notification will say, "Can you feel the sunshine? Does it brighten up your day?". A reference to the song "Can You Feel The Sunshine?" from Sonic R.

Notification #1: https://imgur.com/ErC7dVB


Reference:

Notification #2: https://imgur.com/IvbVt70

Sonic R Portion: https://youtu.be/oY9m2sHQwLs?t=39s