Copyright for Swee'Pea's debut strip was not renewed in 1961 or 1962:

https://onlinebooks.library.upenn.edu/cce/1961r.html

https://onlinebooks.library.upenn.edu/cce/1962r.html

Therefore the character as depicted in the strip has been in the public domain same for other characters that first appeared between late 1930 and possibly 1938, but Popeye himself was renewed. King Features Illustrated Weekly also does not have a date for Swee'Pea's debut when searching Project Gutenberg's renewal records for the specific strip meaning that Swee'Pea's debut strip and possibly the storyline he debuted in was not renewed.

This work is in the public domain because it was published in the United States between 1930 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties. العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/−