I was just wondering, is there a difference of how rare it is to get certain experiments by zapping? Are there some more 'common' experiments? I've been trying to get an Experiment and during that I've gotten and at least twice each or even more, and none of the others.

Nope. :)

I've gotten pretty much every one BUT the one I want () in the past year of zapping. No idea how much tokens it took. Sometimes the zapper just hates you, be patient. XD

Best of luck :)

I guess I really just need to be patient. Funny, the zapper almost never gave me experiments with my other pets... and now that I want them, he constantly gives me some of them - except the right one!

It does it in turns with me. First a fit of random experiments, then lots of hunger/happiness/malunction... rinse, repeat.