One of the most popular and grand period dramas ever made, so much of Downton Abbey's appeal comes from its elegant sets, costumes, and escapism. However, the lasting appeal of the series reaches far beyond the beauty of the show. It's the relationships between the characters that keep audiences hooked.

Obviously there's the romance, but many the friendships in the series are just as engrossing. There are just as many friendships that we love to watch though as ones we hate. Here are some of the best of the series along with some of the worst.

RELATED: Downton Abbey: Main Characters, Ranked By Intelligence

Worst - Thomas and Andrew

Thomas Barrow is one of the most complicated characters in the show. For so long he was nothing more than a foil for the more likable characters, but, as the series went on, his sympathetic nature overcame his worst intentions.

Sadly, even his best sides couldn't appeal to characters with innate biases. Watching him and Andrew stumble through their friendship, with Thomas being forced to walk on eggshells constantly, was a nightmare.

Best - Mr. Carson and Lady Mary

This friendship overcame age and time to be one of the most lovable in the series. Mr. Carson and Lady Mary might not have had as much screen time together as others, but, every time they shared a moment together, you could feel the love and warmth.

It was a great pseudo-grandfatherly relationship between the two in a family where one didn't exist. Probably the best moment between the two of them was when Carson consoled Mary after Matthew's death and was the only one to bring her out of the darkness.

RELATED: Downton Abbey: 10 Worst Episodes Of The Show (According To IMDb)

Worst - Anna and Bates

When it comes to friendships and couples, Anna and Bates seem to cause one of two reactions. Either fans love them for all the struggles they overcome, proving time and time again that their friendship and love can endure anything or you're a sane human being who realizes how toxic these two really are.

Anna is a great character, with a strong moral backbone and what was once believed to be a strong direction. Yet, Bates constantly commits sketchy—if not illegal—acts. When your wife believes that you might have murdered someone twice, perhaps the stability of your friendship and marriage might need to be reevaluated.

Best - Molesley and Baxter

The trope of will they or won't they get together among fictional characters is one of the oldest in fiction. It has become a staple though of a lot of lazy writing, leaving many viewers to dislike the practice. But, when it comes to the friendship of Molesley and Mrs. Baxter, it is done perfectly.

The pair became really great friends first, with Molesley serving as a great first friend to Baxter in Downton. At this point, after multiple innuendoes-filled interactions, even the characters themselves don't know the exact points at which they stand with one another, and that's just fine. The ambiguity in regards to their romance takes a backseat to their strong friendship.

Worst - Simon Bricker and Cora

The relationship between Cora and Robert is one of the most inseparable in the show. So, whenever the writers decided to put it to the test, it seldom worked out. These two are so strong most of the time, it was unfathomable that either would be unfaithful.

When esteemed guest actor Richard E. Grant joined the show as Cora's very romantically inclined art friend Simon Bricker, we couldn't wait for this plotline to be nipped in the bud. Cora showed time and time again that she would never be unfaithful to her husband, so why did the writers want to attempt this song and dance? It was a waste of a great actor in a role that served little to no purpose.

Best - Daisy and Mrs. Patmore

The relationship between Daisy and Mrs. Patmore was one that lasted the entire series. From the beginning, the two were intertwined, with Mrs. Patmore serving as the mentor in the Kitchen to Daisy. While their relationship was fairly rocky at the beginning and still weathered a few weary storms throughout the show, they always stayed close.

Their relationship became that of a mother and child, with Mrs. Patmore becoming the ultimate figurehead in Daisy's life. With the two of them behind the wheel of Downton's kitchens, they soon became part of the houses themselves. Downton Abbey wouldn't be the same without a friendship like theirs.

Worst - Ms. Bunting and Tom

Tom is a frustrating character in that he is so likable yet so confusing in his characterization. The concept that his politics would change over time makes sense when it comes to his relationship to the Crawleys, but the fact that he flip-flops between his radical self and newfound wealth is staggering.

So, when Ms. Bunting arrived, she served as a gateway for him to leave the show. He could have joined her and remained true to himself as an Irish Revolutionary. Instead, he was dragged along with her for a whole season only to let her go at the final moment. It was a wasted friendship.

Best - Violet and Isobel

This has got to be one of the most iconic friendships in the history of television at this point. For many, Maggie Smith's Violet Crawley is the face of the series, defining each moment with some of the best-written insults of any series. So, to serve as her argumentative foil is Penelope Wilton's lovely Isobel Crawley.

The two spar amazingly in the early seasons, serving as polar opposites. But, as they show grows, so does their friendship. While they thrive on their arguments, they really do grow to care about each other very much. The two become inseparable friends, serving as the elders to the proceedings at Downton.

RELATED: Downton Abbey: 10 Hidden Details of Violet Crawley's Costume You Didn't Notice

Worst - Thomas and O'Brien

These two were the biggest headaches in the early seasons of Downton. While they were really solid villains, in retrospect they were both awful companions to each other. Their entire friendship was based on the suffering of others. They thrived on the pain they caused through their manipulation.

So, when O'Brien left in the middle of the night never to be seen again, it seemed that we were free of their treachery. Don't get us wrong, we enjoyed their moments of sparring, but, since O'Brien left, Thomas became a far more compelling, if not the most compelling, character on the show.

Best - Mr. Carson and Mrs. Hughes

This friendship might be the heart of the entire series of Downton Abbey. Mr. Carson and Mrs. Hughes are two halves of one coin, overseeing the day to day operations of Downton Abbey. Though they are a great team, they are anything but an echo chamber.

Mrs. Hughes is far more critical of the proceedings of the Crawley family and isn't afraid to speak her mind about it. In contrast, Mr. Carson is beyond reverent to the Crawleys and tradition. This combination of opposing beliefs is anything but detrimental to their friendship, as it brings them so close that they eventually fall in love. They are one of the sweetest partnerships one could find.

NEXT: Downton Abbey: 5 Couples That Are Perfect Together (& 5 That Make No Sense)