Imagine a child drawing a picture of an elephant. Now imagine how the child feels when you look at it's drawing of an elephant and say "What a fantastic drawing of a squirrel!"
From what you say about the context, it seems to be used as a sarcastic comment on the quality of someone's design. "Your design is a fantastic squirrel" means it's about as useful as a drawing of an elephant that looks like a drawing of a squirrel.
Thank you liliput,
That is a wonderful and clear description. I'm sure you're right about the origin of the phrase.
It looks to me like someone liked the phrase and is collecting examples of it's use, not necessarily related to it's origin. Squirrel can be used in cooking, those might be good recipes. Squirrels are a nuisance, an effective repellant would be a valuable product.