This page contains information on all known Easter Eggs and References located within Celeste. If you have found any such references, please let us know and add them using the EDIT button.
The Crystal Heart in Chapter 4 can be a tricky one if you don't know that it's actually a reference to a secret in Super Mario Bros. 3.
A white block can be found at the bottom of the screen that looks identical to a white block found in World 1-3 of Super Mario Bros 3. In Mario, holding 'down' on that block for about five seconds will drop you through it and into the background of the level.
Similarly, holding down on the white block in Celeste will drop you through it. From there, you can hop on the background art as if it were solid to climb up and reach the Crystal Heart.