John Leguizamo was actually bitten by the snake during one of the takes where the snake is slithering up his leg. When the snake bit him, it wouldn't let go, so the trainer had to pry it off of his leg. When it finally got off, John was rushed to the hospital to remove the fangs which were still stuck in his leg.
The song that Pest sings during the opening sequence is an adaptation of "Rapper's Delight" by the Sugar Hill Gang.
John Leguizamo really wanted to make a movie, so he and his best friend at the time, writer David Bar Katz, came up with the idea for The Pest and wrote a treatment together. Leguizamo bet Katz $1,000 that he couldn't write the screenplay for it. Then, Katz had it written in three days. It also should be noted that Katz had never written a movie prior to this. Leguizamo wrote a lot of the gags in the film such as the opening shower sequence. Leguizamo later admitted that now he "would probably do things a little differently", like spending a month on the script instead of just three days, and that he "kinda fucked up".
The bird in the opening song was John Leguizamo's actual pet bird and would take it along with him everywhere.
The opening shower scene was shot over two days.
David Bar Katz: the writer appears as the man outside the Paris Club who says, "Parties are never "mad," they're angry."