Canon, a random kid who had a crush on Frankie crated an imaginary friend who was looked exactly like Frankie but dumber, more passive and way more trusting of other. Frankie was disturbed by this.

I think this even gave rise to the theory that in the Foster's universe it's likely lonely teens and adults just imagine imaginary friends based on celebrities or people they're sexually attracted to for the sole purpose of sex. Obviously the show itself wouldn't explore such a topic since it was made to be family friendly, but I imagine a version of the show made for adults would legit explore such a topic.