Reader question! Hooray!

Slightly delayed because goddamn roommate.

A reader submits to me two adorable PBS Muppet videos -- one with Tom Hiddleston and one with Benedict Cumberbatch -- and comments:
Comparing the two, I wonder if Cumberbatch is slightly ill at ease, possibly preferring to act alongside flesh-and-blood, because Hiddleston seems more comfortable in his segment. Possibly because he's improvising more? What do you think?
Not really. I think what you're seeing there is a difference in acting styles and scripts. Hiddleston's segment casts him at someone who's obviously familiar with Cookie Monster already -- and besides which, he spends the entire time trying not to go heeeeeeee heeheehee Muppets! -- while Cumberbatch's script is specifically asking him to be bewildered by Murray's insistence on being his arch-nemesis and refusing to get his name right. Cumberbatch generally reads very true when he's acting, and in this case he's playing himself, so you get a convincingly awkward and confused performance.

Muppets are noted to be among the easiest SFX to work with, because the puppet is actually, physically there to look at and talk to. Muppet voices aren't dubbed in post; they're still produced in real-time, which is why the voice artist is also the puppeteer. (Main puppeteer, for Muppets that require more than one operator.) As a side note, this is also why most of the Muppets are left-handed -- the voice actor is using their dominant hand to work the face and match the mouth movements to the dialogue, and their off-hand for working the rod that controls the arm(s). In many respects, it's more like bunraku than western puppetry like Punch & Judy. Some of the more sophisticated models used in the movies involve animatronics, but for the most part, there's still just a guy behind the podium with both of his hands jammed into a really big puppet, who can react, on set, to their co-stars just like any other actor.

Both Hiddleston and Cumberbatch have done greenscreen work, and Cumberbatch was doing motion capture for, as well as voicing, Smaug in The Hobbit. Both of those are on the opposite end of SFX from Muppetry. In greenscreen, you have only the other actors (and sometimes some very green props) but not a proper set to bounce off of, and in mo-cap work you have none of the above -- you're generally in a small room of exactly-known dimensions and precise lighting, by yourself, wearing a very silly looking bodysuit that has little reflective bobbly-things stuck on each joint. It's only been recently and at great expense that films like The Avengers could use gridded mo-cap suits in situ for overlaying Tony's Iron Man armor, and to capture the Hulk performance. (Hell, even TRON: Legacy, a proper Disney production released only two years before, gave up and decided that the original's rotoscoping was such a PITA that it was easier to just make everyone's suits light up for real.) Cumberbatch does say he misses having something to react to, but that's not a problem with Muppets, because, you know, plush critter talking to you, live, right there.