Sesame Street has been on the air for 50 years, which for so many of us means that we have had the privilege of growing up with the Muppets who have become household names. There are few characters more irreverent than Big Bird, Elmo, Cookie Monster and the crew. For five decades, the Muppets of Sesame Street have hung out in living rooms all over the world, teaching life lessons to young kids and parents alike.

We'd argue that all of the Muppets are important, especially since they've helped young people understand issues ranging from whether or not it's okay to eat cookies all the time (it's not) to what it feels like to grieve the loss of a friend, but here are 10 Muppets who have been particularly instrumental in teaching parents and children about tough topics over the show's past 50 years.

Karli taught us about foster care and how addiction affects kids.

In May 2019, Sesame Street introduced its newest Muppet, Karli. She's in foster care, being taken care of by her "for now" parents. In October, it was announced that Karli would reveal the reason that she was in foster care: Because her mom has a "grown-up problem" and struggles with addiction.

Lily taught us about homelessness and food insecurity.

In December 2018, the show introduced its first homeless muppet, Lily. Lily had been on the show since 2011, but seven years later, in a response to the rise of homelessness, she admitted to Elmo that she does not have her own place to live. Sesame Workshop announced that Lily's storyline would be used to "offer help and hope to the growing number of young children across the United State who are experiencing homelessness," and created new videos, books and activities for families.

Julia taught us about autism and its various (sometimes harmful) stereotypes.

In March 2017, the show took another step toward inclusion by introducing a muppet named Julia who has autism. When Julia was introduced, it provided an opportunity for the show to explain her differences and strengths to the other Muppets, which means that the viewers are given the chance to learn, as well.

Alex taught us what it was like to have a parent who is incarcerated.

In June 2013, Sesame Street tackled parental incarceration when they introduced a muppet named Alex in their online series, "Little Children, Big Challenges."

Rudy helped teach us about being part of a blended family.

Rudy was introduced in April 2017 as Abby Cadabby's stepbrother, in order to teach kids that families can look different and be different, but still love each other just the same.

Osvaldo taught us about different cultures (he was from Puerto Rico) and was the first bilingual Muppet.

The show has always been ahead of its time, introducing Osvaldo el Gruñón (a.k.a. Oswald the Grouch), a Muppet from Puerto Rico, in 1979. Osvaldo was the first bilingual Muppet on the show; now, Spanish is spoken frequently on the series.

Rosita was the first Latina muppet (and second bilingual Muppet) on the show. She also taught us about military families and deployment.

After Osvaldo, there was Rosita, a Muppet from Mexico who is also bilingual (and full of energy)! She often presents kids with the Spanish word of the day. In 2003, more than a decade after her 1991 debut, it was revealed that Rosita's dad had been in the military and that he needed a wheelchair due to his injuries. In 2012, Michelle Obama and Jill Biden appeared on the show with Elmo and Rosita to talk about military families.

Kami, the HIV-positive muppet from South Africa, brought awareness to HIV/AIDS.

Kami, a Muppet from the South African co-production of Sesame Street, made history in 2003 when it was revealed that she was HIV-positive. After the announcement, Kami appeared with the likes of Bill Clinton, Oprah Winfrey, Desmond Tutu, Laura Bush and Whoopi Goldberg, to bring awareness to the cause. Kami taught children lessons about the disease, such as how it can (and cannot be) transmitted and how to handle the loss of a loved one.

Aristotle taught us about what it is like to be visually impaired.

In 1982, the show introduced Aristotle, a blind Muppet who helped his friends to understand that a visually impaired person can be just as capable as his or her friends with sight.

Abby Cadabby taught us about being a kid whose parents are going through a divorce.

In 2012, it was revealed that Abby Cadabby's parents were divorced, which gave the show the opportunity to teach both the other Muppets and the viewers that children of divorce can have "big feelings," but that divorce is never the fault of the child.

This Story Originally Appeared On People