X-Men #19
I am a big Mimic fan; I always felt like he was a character who never really got treated right. I think a large part of it probably has to do with the dorktastic costume that he was given. This story goes back to that sort where they trick the bad guy using some kind of power-altering ray much like what happened with Unus when he first came on the scene. The Mimic uses a gadget designed by his father to give himself more power, not knowing that it would really take them away.
On a side note, I don't think anyone saw the importance of Beast's line, "I'm beginning to find the company of women somewhat trying" as he and Iceman wait for Iceman's girlfriend to come with a date for Beast.

