xkcd #3310: Rejected Space Mission Profiles
Title text:
Although NASA agreed that Voyager 2 'seemed lonely' they decided against launching a companion orbiter mission after further measurements indicated that the spacecraft actually preferred the peace and quiet.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3310/
Also a crewed Pluto flyby orbiter.