I just tried two easter eggs which are mentioned in these (German) blog post.
The easter eggs work on the VC20, C64, C16/Plus4 and C128 and I was curious about if they also work on the C65/MEGA65. 
Info: Both work only with the original ROMs (I have tried 911001 and 911210).
In order not to spoil the fun, I have deliberately not mentioned the results of the programs in this post. 
If you want to try, I have attached a zipped D81 image with both easter eggs programs. I also had uploaded the disc image on the MEGA65 Filehoster: "Two Easter Eggs in BASIC 10"
