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/
Someone wrote a paper about sample return mission to Pluto
https://www.scribd.com/document/92881455/MITEE-Nuclear-Engine-for-Mission-Pluto