[Terry D]

"Very like a whale."--Shakespeare

I suppose everyone has their own definition of a unicorn or a whale. Mine fall into several categories.

1. Guys who can't be found with a given club at all (Dave Hostetler, Bob Owchinko, Houston Jimenez, Wayne Nordhagen with the Pirates).
2. Players who can be found with a certain club, but not in a given year. This often boils down to uniform numbers and uniform variations (Phil Manowski with the '82 Mets, for example).
3. Players who have been found, but whose images are marginal or completely unusable for my purposes--too small, too badly photographed or colorized, too heavily autographed, etc. (Steve Dillard with the White Sox, Bernie Carbo with the Pirates, Barry Evans with the Yankees).
4. Players who have been found in minor league outfits that are identical or purty darn close to the major league uniform, but still aren't strictly major league shots (Randy Stein with the Iowa Cubs, Steve Jeltz with the Portland Beavers).
5. Players who have been photoshopped into major league uniforms, often poorly or in the wrong year, etc. An example I saw here is an image of Steve Owchinko as an Expo, which is actually (poorly) photoshopped from an early 80's photo of him with the A's.

As you see, my various classes of baseball fauna may not be the same the rest of you use.