Before Jim Henson was a household name (and to some extent, after), he made commercials to pay the bills. The commercials typically feature early muppets (including a proto-Kermit before he was a frog), and many of them are violent, juvenile, and excellent.
Henson's commercial work started in the 1950s with ads for Wilkins Coffee—ads that were so successful, they brought other coffee companies calling, asking for more of the same, but with their brand added in. Henson's gift was getting a simple message across visually, with humor in the mix.
As the years rolled along, Henson made commercials for phone companies, cereal companies, meat companies, gas stations, IBM, you name it. Here's an insane 37-minute reel compiling tons of his early work, along with hilarious tongue-in-cheek behind-the-scenes bits. Just sit back and watch the master at work.
Be sure to check out 35:58, where ads for Munchos potato chips feature a chip-eating monster who would, with minor retooling, become a star. (Henson retained ownership of his characters even when doing commercial work, which allowed him to build up a stable of characters including Kermit, Rowlf, Cookie Monster, and more as he went!)