Two aliens come back to earth to check up on humans, who they once helped overcome global warming and general extinction of all life due to contamination, only to find out that some things may still need a change.
1988
1995
1990
2018
2002
1956
1973
2004
2024
1989
2001
1978
1984
1985
1997
1992
2006
2008
2023
