Smile Time Puppets

The Smile Time Puppets were the chief antagonists of the highly acclaimed Angel episode "Smile Time" as well as the spin-off comic books that came after the episode's success - they are also unique in the fact that they are Muppets akin to those seen in Sesame Street or other Henson media, of course unlike their harmless real world counterparts these muppets were malevolent and twisted, being possessed by demons that sought to use them to cast a spell over their young audience and drain them of their life essence.

Polo
The leader of the Smile Time Puppets and seemingly the most sadistic, he enjoyed luring children to the screen of the television so that he could drain them of life energies - at the same time he and his "friends" used magic to hypnotise their audience, leaving them vulnerable to the assault.

Polo fought Angel while the vampire was trapped in a muppet form and was defeated when Angel (still in puppet mode) somehow managed to activate his vampiric power and tossed Polo right through the set.

Groofus
Perhaps the one Smile Time Puppet who actually acted like a muppet, in the traditional sense, he geniunely wanted to provide entertainment and education for children - unlike Polo, who simply saw them as something to feed off: at the same time however Groofus was a demon at heart and went along with the actions of his brethren, he was decapitated during the climatic fight and was more concerned with the fact Angel and his crew were "ruining the show" than the fact that his brethren were going to massacre hundreds of children.

Ratio Hornblower
A bizarre demon that took the form of a full-bodied muppet, he was the mystic of the group and tended to the devices that kept Smile Time running - despite this he seemingly couldn't talk and was killed by Fred and Wesley in a flurry of violence (which was really just a lot of foam and rubber, since Ratio - like the rest of his brethren - was not a living creature)

Flora
Not much is known about Flora save for the fact she seems to be the sole female of the group - she is also one of the more humanlike muppets, like Polo she is sadistic as she was seen torturing her creator Framkin alongside Polo via literally turning him into a human hand-puppet.