The Vikings were a historical Scandinavian people, best remembered as sea-faring raiders. Outside of the Muppets, Vikings can still be found in Minnesota.
Link Hogthrob and the pigs portrayed Vikings for a musical number, "In the Navy," in The Muppet Show episode 524.
A group of Whatnot Vikings were also featured in The Muppets Celebrate Jim Henson.
On The Muppets' episode "Too Hot to Handler" Fozzie Bear records a couple of regional promos for Up Late with Miss Piggy. In the one for Minnesota, he poses as a viking.
In the German Sesamstrasse spin-off TV-movie Die Zeitmaschine, characters Wolle and Pferd accidentally time travel to a group of Vikings for an adventurous interlude.