Example 1 (aka A FLIPPING DISASTER):

- Literally just a mashup of the two parents.

- Uses the exact same colors from Cheese Sandwich and Pinkie Pie.

- Splotches and markings when nopony in their family has them. (I usually add markings ONLY IF one of the parents has them. Examples: Pipsqueak, Troubleshoes and Sunburst)

- Mane looks exactly like one of the parent’s manes.

- Has mismatched eyes. (I’ve seen very few foals that can make that work, like Lopoddity’s Aerostorm for example.)

Example 2:

- Mane is a bit more original.

- Used colors from various other family members to create a more original color palette. (I made this gal by playing around with Cheese and Igneous Rock’s colors.)

- Isn’t obvious who the parents are and could easily pass off as a non-shipping OC.

Be sure to keep this in mind when designing a fanfoal. And as I mentioned, don’t be afraid of creativity.