One of the last lines in the episode "Send in the Clones" (episode 128, season 6, episode 16).....

"Hey, we could do someone else [clone them]. You know, I've got some of Dr. Spock's toenails at home from when I was a Trekkie?"

Having heard the line for myself, I looked up the script on a fansite. Lo, and Belhold! There it was. I find it hard to believe that SOMEONE didn't catch this one. I think that any Trekkie would be highly disappointed with the result of cloning DR Spock, the "father of modern parenting" instead of MR Spock.......

The proof? See the offending dialogue below.....

and the website with the transcript......

Mack: "Hey, do you guys think they're gonna believe us at the conventions?"

Lea: "Are you kidding?"

Polly: "Not a chance."

Mack: "Hey, we could do someone else. You know, I've got some of Dr. Spock's toenails at home from when I was a Trekkie?"

Lea: "You were a Trekkie?"

Mack: "Yeah."

Lea: "You really are a nerd."

Mack: "Hey, I'm not proud of it, okay?"

http://www.whoosh.org/epguide/trans/616trans.html