I'm sorry, but "X didn't have any speaking lines" is BULL! It's obnoxious fan nitpicking, and we should at least be thankful we even got that one line out of X character.
Remember when Dr. Teeth said "Shalom" in MFS and it was the greatest thing ever? Or same movie when Scooter was selling T-shirts? That was the most we've seen of those character since the last Henson project before he died. The fact they were even in that movie, let alone The Muppets, was amazing.
Here's the deal. The film had way too many Muppets in it. And for each of them to get a big moment of glory would have killed any semblance of story. I mean, they shoved enough in a 90 minute film as it is. Yes, it would have been awesome for the Mayhem to have a song all to itself, the first one since "You can't Take No for an Answer" (unless you count the mostly instrumental Nap Time from MWO)... but they didn't even have time to have the 30 seconds of plot reveal in the villain's song.
Meanwhile, Link Hogthrob gets his first major speaking (well, singing) sequence in a movie ever. Where's the appreciation for that? Let alone Wayne and Wanda's make out session. Characters that haven't been seen (not counting the comics) since The Muppet Show.