What do you call an awkwardly unfunny and cringeworthy person?

That person who tries to act funny or "cool", but he turns out to be cringey and tacky instead. What do you call that person?

Example: Look at Todd, interfering in our conversations, telling us jokes about chickens crossing the road and failing to make us laugh. I cringe when he does this. He is just so [insert word].

Typically, it would be considered tactful to describe such a person as awkward or socially awkward.

As an example: 6 Signs That You're Socially Awkward from People Skills Decoded.

There are also a lot of offensive/insulting terms, including terms like weird, creepy, and socially retarded. I wouldn't recommend using those.

You can say 'dorky', though it may be offensive to some people.

Dorky: awkward and stupid.(Cambridge Dictionary)

;or a 'dork' (a contemptible, socially inept person- from google dictionary) as in "He's such a dork."

I like the word buffoonish.

Look at Todd, interfering in our conversations, telling us jokes about chickens crossing the road and failing to make us laugh. I cringe when he does this. He is just so [buffoonish].

A Brief History of the Buffoon

In English drama, the buffoon was analogous to one of the three stock characters in ancient Greek drama, the Bômolochus, and the other two were the Eirôn and the Alazôn.

The Bômolochus was the character who was marked by his wit, his crudity of language, and his frequent non-illusory audience address. (Interestingly, in modern Greek, the word refers to a foul-mouthed person.) The Eirôn was the ironic fellow who acted as if he knew less than he actually knew, and his counterpart, the Alazôn, acted as if he knew more than he actually knew.

Good Old Boys: "Ange" and "Barn"

A fairly modern appearance of the three stock characters is from The Andy Griffith Show, which was a popular TV show in the 1960s (and is in syndication in the US to this day). Don Knotts (now deceased) played a bumbling buffoon as Deputy Sheriff Barney Fife, and Andy Griffith (now deceased) played the people-smart sheriff without a gun, Sheriff Andy Taylor.

I say three stock characters because Barney Fife and Andy Taylor played a sort of combination of all three characters from Greek drama, and actors Don and Andy played humorously (and very successfully) off each other for a number of years.

Since Sheriff Taylor considered Barney (or "Barn," as he often called him) to be his best friend and not just his employer, he did not very often take umbrage with Barney's shenanigans. More often than not, however, the general citizenry of the town of Mayberry (the duo's bailiwick) treated Barney like a buffoon, making fun of his officious, know-it-all attitude and actions.

Andy as the Eirôn would often string Barney along, obviously for comedic effect, and at the opportune time burst Barney's bubble by exposing his braggadocio, much as Socrates would in one of his dialogs.

In concluding my expansive rambling, I think the word buffoonish is just the right word for the person you describe. Unfortunately, however, the current denotation of buffoon is simply a clown, and the person you describe is more than just a clown.

Although it is possibly a British-exclusive usage, I would call them a twit. This is definitely pejorative.

A silly, annoying person.

Typically...how about atypical.

Other definitions of socially inept people often stereotype those with Autistic Spectrum Disorder (ASD). High-functioning people with ASD are sometimes said to have Asperger’s Syndrome.

If the person is ASD, I would cut him some slack, and try not to isolate them socially any more than they already feel.

If Todd has come to terms with ASD, we could just say:

That’s just Todd, being Aspie/Autistic.

While I typically refer to these people as jackasses, you would probably do better to describe this person as a try-hard

A person who puts a large amount of effort into achieving a certain image, or counter-image, to the point where it is obviously contrived. Rather than achieving an image through genuine personality, the try-hard consciously attempts to fit a certain style through deliberate imitation, forced style, or scripted behavior. That is to say, he/she is trying hard to create an image.

Source (unfortunately): Urban Dictionary

The try-hard (sometimes stylized as tryhard) can occasionally try to fit in with such desperation that it creates a reverse-appeal.