VIDEOS:
The Mara - 1982 vs 2011
A number of 1963-1989 Doctor Who serials' home media releases give viewers the option to watch the stories with redone/upgraded special effects. Shown here is a comparison between the broadcast version of "Kinda" and the enhanced version on the 2011 DVD, which replaces the Mara's rubber prop with a more animated CGI snake. This clip is taken from the now-dormant official YouTube channel for the Classic Series.
Example of:
Enhanced on DVD