A court fight between corporate heavyweights Kellogg Co. (NYSE:K) and Exxon Mobil Corp. has been reignited over the use of cartoon tigers in advertisements of food items.A federal appeals court has reinstated the lawsuit by Kellogg, the cereal maker, challenging Exxon's use of a cartoon tiger to promote food and beverage sales at its convenience stores. The decision last week by the 6th U.S. Circuit Court of Appeals reversed a 1998 pretrial ruling by U.S. District Judge Julia Gibbons, of Memphis, Tenn., who ruled in favor of Exxon. The case now returns to Gibbons for reconsideration.Exxon and Kellogg spokesmen did not return telephone calls seeking comment Wednesday on the appellate court's ruling.Both Kellogg, based in Battle Creek, Mich., and Exxon, based in Irving, Texas, have used cartoon tigers to advertise since the 1950s.Kellogg used its Tony the Tiger symbol to promote cereal sales and Exxon used its "Whimsical Tiger" to promote sales of petroleum products. After Exxon began using the tiger in ads to promote food and beverage sales at its convenience stores, Kellogg sued Exxon in 1996.Exxon argued that Kellogg had acquiesced to Exxon's advertising use of its tiger. In 1968, Kellogg asked Exxon not to oppose Kellogg's application to register its Tony the Tiger trademark in Germany. Exxon's "Whimsical Tiger" trademark, obtained with no opposition from Kellogg, became legally incontestable in 1970.Kellogg argued that Exxon progressively infringed on the cereal maker's use of its Tony the Tiger by increasingly using it to boost sales of food items.