Johnasson played a pregnant schoolgirl in a skit poking fun at MTV's My Super Sweet 16 and 16 and Pregnant shows.
In another sketch, the Lost in Translation star played a schoolgirl in full uniform in a spoof Disney drama, forcing a friend with a broken knee to take her to the prom and dance with her.
Johansson in her monologue offered advice to younger Hollywood stars trapped in the spotlight, before singing 'Class' from the musical Chicago, alongside cast members dressed as Dina Lohan and Ke$ha.
"I try to stay out of the tabloids, I am not perfect but I have found a few simple ways for a young celebrity to stay out of the tabloids," Johansson said in her monologue.
"For a start, wear underwear. Why wouldn't you? It takes seconds to put on and it's comfortable. Underwear - it's your friend.
"If you make a sex tape you are not allowed to act surprised when it ends up on the internet. Sex tapes are like takeaway soup containers, they always leak."