Laszlo the Artist is a one-off character from Rugrats.
He was a French artist who used a woman named Mrs. Chesapeake to model for a portrait and after he had finished, he invited her back to his studio in a building to see it.
Mrs. Chesapeake arrived was very excited to see it. He asked her to cover her eyes whilst he set the mood for the moment, with some music and a table with lit candles and a bucket of champagne in ice.
Unfortunately Tommy Pickles got into the studio and stepped on a tube of black paint, that splattered on the portrait to resemble a moustache and beard, ruining it.
Not realizing what had happened, he finally allowed Mrs. Chesapeake to open her eyes, and she screamed at the sight.
After this, he is not seen again, but you can guarantee he was just as much upset by the sight as she was and judging by the way Mrs. Cheasapeake furiously left the building, it can be assumed she did something unpleasant to him afterwards or threatened to sue him for the insulting portrait.