The California congressman was doing an interview Monday on MSNBC's 'Hardball' with host Chris Matthews -- and while he was going on and on about Ukraine and alleged malfeasance by DT ... something that sounded like a loud, wet fart blasted through the airwaves.

It certainly seemed like flatulence, and Rep. Swalwell even paused a moment right afterward in what many viewed as an acknowledgment of the ripped gas. And, of course, #fartgate and #shartgate soon started to trend everywhere on Twitter as a result.

Funny enough, the official 'Hardball' account excused the noise away as someone dragging a coffee mug across a table in the studio -- which just happened to get picked up on a mic.

Swalwell was ecstatic, quickly using the network's cover as what he described as "TOTAL EXONERATION!" -- very Trump-like, right?! And yes, everyone had a good laugh over it -- Republicans and Dems alike. It might've been the most uniting thing in a while, actually.

And, for those looking to go even deeper down the rabbit hole ... some have pointed to a theory that the would-be fart actually came from Matthews. Apparently, there's a history of gas being passed on his show over the years, as one Twitter user dutifully pointed out.

Anyway, if these impeachment hearings are lacking pizzazz -- as NBC News itself noted last week -- then Swalwell (or Matthews) just dropped a much-needed fun fart bomb.