The game is very similar to this except it's impossible to do it all in 90 seconds here.
Rules are simple: starting person makes a scenario and starts a sentence with a letter. The next person starts another sentence with the next letter, the person after that does the same and so on. When we eventually reach the starting letter, the person who hit that letter creates a new scenario, picks a new letter, and it starts over.
Example: (starting letter = B, scenario = the office building's on fire) Person 1: "Bring me this month's financial reports." Person 2: "Can't you see the building's on fire?" Person 3: "Does it matter?" Person 4: "Everyone else is evacuating."
Ok now it starts Scenario = You're on the Titanic when it crashes into the iceberg; Starting letter = J
Ahh!!! Well we have reached A, so here is the new scenario: You are trapped in a warehouse with a piece of pie in the middle of the room. However, if you eat the pie, you die.