I had to weave and play around with a honey bear, you know, and I could wrestle with him a little bit, but there's no way you can even wrestle a honey bear, let alone a grizzly bear that's standing ten feet to eleven feet tall! Can you imagine? But it was fascinating to work that close to that kind of animal.

He was interred in Fort Lauderdale's Evergreen Cemetery. In the Seattle Post-Intelligencer Nielsen pointed out that he remembers Curtiz as "a sadist a charming sadist but a sadist".

Nielsen's performance in the films Forbidden Planet and The Poseidon Adventure received positive reviews as a serious actor although he is primarily known for his comedic roles during the 1980s and the early 1990s. Nielsen made his film debut in 1956 and began collecting his roles in dramas westerns and romance films between the 1950s and the 1970s. Nielsen's portrayal of comedic characters seemingly oblivious to (and complicit in) their absurd surroundings gave him a reputation as a comedian.