Bad improv causes 300,000 deaths per year, which is more than Black tar Heroin according to a statistic I made up.
AKA: The Harold, The Armando
Audience members is asked for a suggestion. Typically, the suggestion is one of the following: Gay, Queer, Fag, Penis, Vagina, Fart, or Babylonia. A member of the Improv troup, anywhere between two to 1,400 people, steps forward and tells a humorous monologue drawn from real life experience, or, more painfully & typically, a chunk of that improv troupe member's stand up routine. Sometimes they begin with a meandering word association game that know in the audience can understand. Or, sometimes animal noises. The rest of the troupe listens patiently and is expected to pull humourous parts of the story/random phrases/noises to create a sketches that, hopefully, interconnect. What's amazing is that all of this is done despite the crippling anxiety and depression of the performers who went into improv because they couldn't get real acting work/they are unfunny stand ups.
Damn near every god-fearing sketch comedy show you have ever seen. A short list: SNL, UCB, SCTV, and other initialisms!
AKA: The Shortie, or Whose line is it anyway?
This is what everyone thinks Improv is, i.e. short scenes in which performers try to find the joke fast. Theater games are typical like "World's Worst", "Freeze Tag", Etc. Although, those are more typical in theater sports. Sometimes, Short-form works. Sometimes, it doesn't and is then hosted by Drew Carey. Hey oh!! But, seriously, when it doesn't work it is physically painful to watch. It is also typically started by getting suggestions from the audience, but since the games are faster, there are more audience suggestions so you get to hear more people screaming obscenities. Short-form can also consist of sketches but the sketches don't necessarily relate to each other, or dare I say to anything resembling anything suggested by the audience, and might even have been written and rehearsed beforehand(you know who you are you cheating basterds). Bad long-form can seem like good Short-form. Bad short-form can seem like theater sports.
Whose line is it anyway?
AKA: Theatre Sports
Two teams enter. One team leaves. The other team then also leaves, but they are covered in flop sweat, shame, and the reak of failure. It is very, very similar to Short-form. But played with teams.
Whose line is it anyway? (There aren't many Improv shows on TV)
AKA: What the fuck are you doing on the God Damn Subway?!?!?
Typically the performers go out in public and do something strange and improvised.The performance doesn't take sugestions from the audience, it is developed in the field. Upright Citizens Brigade sort set the ball running on this and it took off. Performances typically end when the participants either have to flee from the police or are arrested.
Flashmobs. Also, the Orange Revolution of Ukraine.