No it was just a fun appearance that wasn't promoting anything. Well I take that back it really promoted just the Muppets being the Muppets. They did a huge shout out to the Electric Mayhem and most of its members with the exception of Floyd and Lips. They did a wonderful nod to Kermit and Piggy's relationship, and also noted to two wonderful Muppet songs Being Green, and Man or a Muppet.
Overall, I would have to say that this right here is how you do a Muppet appearance on a late night show. Kermit was sharp witty and funny. Him and Corden seemed to have a good time and worked well together.
Matt Vogel did an excellent job, he is Kermit now and is doing a wonderful job.
Great stuff I give it a 5 out of 5!