I Can't Believe It's Not Butter!
The J.H. Filbert company, based in Baltimore, Maryland, developed the product in 1979 as a low-cost alternative to butter for the food service industry. The name originated from a comment by the husband of a company secretary as he sampled the product, and it was first marketed to retail consumers in 1981. The company was acquired by Unilever in 1986. Unilever expanded sales of the product, previously only available primarily in the Washington, DC/Baltimore area, throughout the entire United States in 1988, and later to the United Kingdom, Canada and Mexico in 1991. The product was put on the market in Germany in 2011 and in Chile in 2012.
In addition to a regular and 'light' spread, Unilever also uses the brand name to market a liquid butter substitute contained in a spray-bottle. This product is an emulsion of vegetable oil in water formulated with a 'hint' of butter flavor (derived from buttermilk) and is marketed as having zero calories and zero fat content. In 2017, Unilever announced two new varieties, "It's Vegan" and "It's Organic".
It was reported in July 2005 (per research from the market research company Information Resources) that the product at that time led in product sales for its category of margarines, butter blends and spreads at $244.7 million USD, summarized from 52 weeks up to July 10, 2005.
But by 2012 the situation had changed. It was reported in 2012 by Euromonitor International that while sales of butter and spreadable oil fell, margarine sales increased by 1.1 percent but sales of I Can’t Believe It’s Not Butter fell by 3.9 percent. 7 percent of sales at Unilever consists of spreads with a significant amount consisting of butter substitutes, the sales of these which are on the decline.
In 2016, there have been $248.4 million in sales of I Can't Believe It's Not Butter and $47.7 million of I Can't Believe It's Not Butter Light. 
In February 2017, Unilever rebranded the product as "I Can't Believe It's So Good... For Everything!" in the UK. The stated objective was to increase awareness of the product's versatility. The rebrand was greeted with puzzlement and some derision by many media commentators. Subsequently the branding was simplified to "I Can't Believe It's So Good...".
- Lazarus, George (June 1, 1981). "Filbert can't believe you won't like its new butter blend". Chicago Tribune. ("Filbert has moved into the Syracuse, Albany, and Pittsburgh markets with a one-pound blend called "I Can't Believe It's Not Butter."") (subscription required)
- Calvani Terry. Antiturst Law Journal, 1989, "Advertising Regulation: The States v. FTC. "...a nationally distributed butter substitute, 'I Can't Believe It's Not Butter.'")
- Cerklewski, F.L. Journal of Food Composition and Analysis, 2005, "Calcium fortification of food can add unneeded dietary phosphorus". "...and butter substitute (I Can't Believe It's Not Butter..."
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- Wyman, Carolyn (2004). Better Than Homemade: Amazing Foods That Changed The Way We Eat. Quirk Books. pp.50-52. ISBN 1931686424
- "I can't believe it's not Butter!". Unilever(United Kingdom). Archived from the original on May 13, 2012. Retrieved April 30, 2012.
- "I Can't Believe It's Not Butter". Unilever (Canada). Archived from the original on April 17, 2012. Retrieved April 30, 2012.
- Jones, Geoffrey (2005). Renewing Unilever: Transformation and Tradition. Oxford University Press. pp. 102-03. ISBN 0199269432
- Elliott, Stuart (July 26, 2005). "I Can't Believe It's Not a TV Ad!". The New York Times. Retrieved April 29, 2012.
- Amanda MacMillan. "Better: Butter-substitute sprays". Health Magazine. Retrieved April 2, 2014.
- "Margarine : Unilever can't believe it's not selling". Bloomberg. July 31, 2013. Retrieved 29 July 2016.
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- "I Can't Believe It's Not Butter is getting a new name - and it's even longer". 2017-01-21.
- (Staff report) (June 16, 2006). "Fabio, Longtime Margarine Champ, Passes Crown to New Spokeshunk". New York Observer. Retrieved April 30, 2012.
- Marikar, Sheila (May 17, 2011). "Kim Cattrall on 'Sex and the City,' Hollywood 'Mania' and 'Having It All'". ABC News. Retrieved April 28, 2012.
- Cerklewski, Florian L. (2005). "Calcium fortification of food can add unneeded dietary phosphorus". Journal of Food Composition and Analysis. 18 (6): 595–598. doi:10.1016/j.jfca.2004.05.003.