|“||You're wasting your time. Factoring in sleigh speed, time zone changes, and reindeer bathroom breaks, it is scientifically impossible for this so-called Kris Kringle to deliver gifts to the approximately one billion qualifying children. As you can see, X equals no stinkin' way.||”|
— Lisa on why she doesn't believe in Santa Claus
Lisa Marie Loud is one of Lincoln Loud's ten sisters in the Nickelodeon animated series The Loud House. Although she is the second-youngest of the Loud siblings, at only four years old, she is also the smartest, having graduated college with a PhD and received a Nobel Prize despite her age. Speaking with a lateral lisp, Lisa spends her time invested in research, projects, and working on complex experiments, which often involve using her siblings as test subjects.
Lisa's first time appearing in a Christmas production is, of course, The Loud House's Christmas episode, "11 Louds a Leapin'". Early on in the special, Lisa expresses disbelief in the existence of Santa Claus, showing her notes about this, and continually remarks to Lola that she is only wasting her time trying to get herself on Santa's nice list. Perhaps because of this, she is noticeably the only Loud sibling who does not have a Christmas stocking hanging on the wall. When Lincoln tells his sisters all about Mr. Grouse being unable to visit his own family for Christmas, Lisa, who normally doesn't show her emotions, breaks down crying after hearing his story. After the Louds and the McBrides present Mr. Grouse with a bus card so he can see his family tomorrow, and he allows them to spend Christmas Eve with him, Lisa responds by crying tears of joy. On Christmas morning, Lisa, having received a piece of a meteorite, admits to her family that she now does believe in Santa, as she managed to get a photo of Santa (actually Mr. Grouse dressed as Santa) leaving a present for Lincoln behind the couch.
In the online-exclusive Loud House short "12 Days of Christmas", in which the Loud family sings their version of the titular song, Lisa sings that her gift was "ten beakers mixing." The first time she says the line, she mixes a chemical that blows up in her face.