"I'm not here to be your buddy", McCarthy tells the press
Saturday Night Live is well-known for taking shots at Donald Trump and his colleagues.
Alec Baldwin made weekly sketches portraying Mr Trump in the run up to the election - but now White House Press Secretary Sean Spicer is in their sights.
Actress Melissa McCarthy is unrecognisable as she dons a wig and a suit to make fun of Mr Spicer.
He has come in for criticism in the past over the size of the crowd at Mr Trump's inauguration, and for insisting the travel ban from a number of Muslim-majority countries was not a ban.
In the piece, McCarthy - as Spicer - takes questions from members of the press played by Bobby Moynihan, Kristen Stewart, Cecily Strong, Vanessa Bayer, Alex Moffat and Mikey Day.
McCarthy is seen shouting at them, telling them: "I came out here to punch you in the face.
"I'd like to begin tonight apologising on behalf of you to me for how you have treated me these last two weeks - and that apology is not accepted.
"I'm not here to be your buddy."
On Mr Trump, McCarthy says: "When he entered the room the crowd greeted him with a standing ovation which lasted a full 15 minutes.
"Everyone was smiling, everyone was happy", McCarthy insists.
While being asked questions, McCarthy picks up her podium and rams it into the crowd.
McCarthy also tells a reporter: "I will put you in the corner with CNN" - a reference to Mr Trump accusing the network of being "fake news".
The sketch also pokes fun at Betsy DeVos, the Trump administration's secretary of education, portrayed by Kate McKinnon.