They Do Exist! is a Christmas-themed M&M's commercial that debuted on TV in 1996 and still airs every Christmas on TV to this day. A follow-up commercial was produced in 2017, but has not been re-aired annually.
On Christmas Eve, Red and Yellow are walking out to a living room to leave a bowl of M&M's candies to Santa Claus. Yellow asks Red if he thinks Santa will like them, to which Red responds by saying he doesn't know, as he's never met Santa before. Immediately upon turning around, they see Santa Claus coming down from the chimney, and Red immediately pass out proclaiming, "He does exist!" Santa, apparently overwhelmed by the appearance of talking candy, also passes out, exclaiming, "They do exist!"
In the sequel commercial, Yellow, realizing that Santa's out of commission right now, takes it upon himself to complete Santa's present deliveries for him. Taking control of Santa's sleigh, Yellow haphazardly tosses gift boxes to all the houses as quickly as he can. Eventually, Santa's elves back at North Pole mission control notice the "nut" in Santa's sleigh and send a phone call to Santa. As Santa and Red wake up, Santa is informed by his elves that the presents are going to the wrong people. We then see various kids confused when they open up their presents or find them in their yards. The people then all go out in the streets as Yellow, having arrived back at the house he and Red were in, is up on the rooftop with Red and Santa, who asks Yellow what he's done. Yellow timidly asks "Did I ruin Christmas, Red?" However, seeing all the people coming together as they exchange their gifts, Red answers, "Actually, buddy, I think you made it even better."