Poor Sam, now that I think about it, no wonder he felt so silly having to sing those parts (even though he didn't know why).
Also, I wonder if Hirake! knows about that connection you've made, aside from the fact that they're both performed by Frank Oz.
After Big Bird told her that he's always grouchy, I don't think she would even try to do so.
Pinkie Pie, on the other hand...