The Nats used the D-backs' bullpen cart six times(!) during their four-game weekend series sweep

By virtue of their 6-4 win over the D-backs on Sunday night, the Nats swept a four-game series from Arizona at Chase Field -- not bad, considering how well the D-backs have been playing lately. 
Cut4 would like to point out to you, dear reader, that members of the Washington bullpen used the D-backs' bullpen cart six times over the weekend. Six times. That brings the season total to seven, factoring in the initial deployment of the cart by Astros right-hander Collin McHugh on May 5. 
This all started thanks to the efforts of Sean Doolittle, of course. The outspoken cart enthusiast rode to the mound on the vehicle before locking down the Nats' 2-1 win on Thursday night. 

On Friday night, the Nats dispatched Arizona again, 3-1, and Doolittle again opted for his favorite method of on-field transportation:

Saturday night's 2-1 win didn't include Doolittle, given the night off after working in the previous two -- but Ryan Madson used it in the ninth inning before preserving the save. 
That led up to Sunday. We'll assume Sean did some lobbying about the cart with his colleagues in the bullpen throughout the weekend, as it got some serious use in the series finale. 

Enjoy that first-person view once more: 

Are we there yet?!?! pic.twitter.com/tfMbO2xlT9

— MLB GIFS (@MLBGIFs) May 14, 2018

Yep, that's right. Brandon Kintzler embarked on his maiden voyage in the cart, Madson used it for the second time and Doolittle for his third trip in as many appearances in the series.
For the mathematicians out there, that's four wins and six bullpen cart rides for Washington on the weekend. Oh, and their pitching staff only allowed Arizona seven total runs in the series. 
Coincidence? Absolutely. But a very fun one nonetheless.