Howard Wolowitz and Sheldon Cooper couldn't be more different on The Big Bang Theory. While they're both incredibly brilliant in their respective fields of study, they're not always smart with each other. Due to their differences, Sheldon and Howard have a hard time agreeing on things, which often leads to disputes in the group. Due to Sheldon's stubbornness, these disagreements never end well.
Despite their contrasting personalities, Howard and Sheldon are true friends and they have many commonalities if they took the time to notice them. It's their similarities and points of interest that keep them together in spite of their differences.
Common Ground: They Love Their Moms
Their common relationships with their mothers aren't spoken about enough. Howard was so close with his mom that he lived with her, bathed her, and did everything for her. Sheldon didn't live with his mom as long as Howard did, but he did rely on her comforting skills whenever he went off the rails. It's surprising that the two characters didn't speak more about their connection to their mothers and how it's impacted their lives as adults.
Totally Different: Their Teacher & Student Vibe Didn't Work
Both Sheldon and Howard agreed on the importance of bettering one's self through schooling. When Sheldon became a part-time teacher at Caltech, Howard decided it was a good opportunity to get his doctorate.
He loathed Sheldon most of the time but Howard couldn't deny Sheldon's brilliance. Sadly, Sheldon's teaching skills and Howard's listening skills didn't match. The two were a mess from the start and it ended with Sheldon calling human resources on Howard.
Common Ground: They're Both Dependent On Their Partners
Thanks to Sheldon and Howard's pride, they'll never admit that they're completely dependent on their wives. They both like to think that they're independent scientists who don't need the comfort of loved ones but viewers know that's not true.
Sheldon realized his dependence on Amy when she went to New Jersey for a couple of weeks for work. Without her around, he didn't have that comfort he was accustomed to. Likewise, Howard leaned on Bernadette for advice, co-parenting, finances, and more.
Totally Different: Their Sex Drives
When it comes to relationships, Howard and Sheldon are essentially different beings. Howard has been chasing women since he learned how to walk but Sheldon didn't care for dating in the slightest.
Howard even broke up with Bernadette for a little to continue playing the field because the allure of "coitus" was too exciting. Sheldon, on the other hand, didn't lose his virginity until the ninth season. And even then, he and Amy were said to only sleep with each other annually.
Common Ground: They Both Lost Their Fathers
Along with being mama's boys, Sheldon and Howard also had similar relationships with their fathers. Howard's dad abandoned the family when he was younger and he never knew what happened to him. Contrastingly, Sheldon's father was around while he was growing up but he wasn't necessarily the best dad. When Sheldon was 14 years old, his dad passed away. This means that both Howard and Sheldon lost their dads are critical ages in their lives, which very well could have had a lasting effect on them as adults.
Totally Different: Would They Be Friends Without Leonard?
Leonard was the glue that kept the group together (although Amy and Sheldon believe Sheldon to be the nucleus). Without Leonard's friendship with Raj and Howard, Sheldon wouldn't have ever met them. It's because of the group's individual relationship with Leonard that they're best friends. Because of this, it's hard to say if Sheldon and Howard would continue being life-long friends if Leonard wasn't around. If Leonard and Penny moved away, would Sheldon and Howard continue hanging out every week? It's hard to say.
Common Ground: Their High School Youths Were Similar
In "The Contractual Obligation Implementation," Sheldon, Howard, and Leonard go back to Howard's high school to talk to female students about getting involved in the sciences. While the three men were roaming the halls, it brought back plenty of memories of being bullied. A student even bumped into Howard and looked at him in a threatening way. When Howard apologized, Sheldon said, "Smart, we don't want any problems." They both struggled with bullying and feeling invisible while in school but focused on their love of science.
Totally Different: Senses Of Humor
It took Sheldon years to understand when his friends were making jokes. Sarcasm was not his friend and it took the help of Penny for him to fully comprehend when people were being dry. Howard, on the other hand, took advantage of Sheldon's confusion with humor and often made him the butt of the joke without him realizing it. Eventually, Sheldon caught on but it was still difficult for him.
Common Ground: Their Love Of Rockets
Even though Sheldon didn't respect Howard's profession as an MIT-educated engineer, he and Howard did share a fascination with rockets. Sheldon was excited when Howard had the opportunity to go to space; he even said to be jealous of him.
In the 11th season, the two came together to build one of Howard's old model rockets. They had a better time than they both expected and drove to the desert to launch the rocket themselves. While in the desert, Howard confided in Sheldon about being nervous about being a father of two, and surprisingly, Sheldon helped calm him.
Totally Different: Working Together Doesn't End Well
Whenever the group put their brains together for the betterment of science, a disagreement typically broke out between Howard and Sheldon. Sheldon usually belittled Howard's degree and intelligence, which then launched a retaliation from Howard. It was neverending. As smart and loving as these two friends can be, working together is not their strong suit.