Bannister Evil Enterprises is a company that is owned by Professor Bannister, serving as the main antagonistic faction in the Phineas and Ferb episode "Sidetracked". It's similar to the evil company Doofenshmirtz Evil Incorporated (owned by Heinz Doofenshmirtz).
Bannister founded the company as he grew sick of Greenland's national anthem and lack of national pride, as it happens to be his homeland. His jealousy of Canada led him to plot his evil scheme there by posing as a Canadian evil scientist. The company also became a sponsor to the villain organization L.O.V.E.M.U.F.F.I.N. when Bannister became a new member of the organization (though it was against the rules for their members to misrepresent their countries of origin, as stated by Doofenshmirtz himself).
Bannister started off his plan by arranging three burglars to steal some parts from Seattle, which he uses to build two magnetic robotic versions of himself (known as Me-Positive & Me-Negative). Two months later, he plotted to steal Canada's symbol of national unity (Albert the Moose), knowing that it would sink Canada's national pride to a new low, which will allow him to annex Canada to Greenland and put in a new national anthem in order to reinvigorate its national pride to a peak. He even got Doofenshmirtz to assist him in his scheme as part of their U.S.-Canadian evil scheme exchange program, though Doof finds Bannister's scheme to be quite complicated in general.
However, Bannister was found out by his archnemesis C.O.W.C.A. Agent Lyla Lolliberry and Perry the Platypus, who were able to defeat his magnetic androids by using their magnetic fields against each other. Lyla and Perry then attempt to capture Bannister, but he uses the Greenland national flag to evade them. Bannister attempted to escape via parachute, but Perry managed to contact his old friend Peter the Panda, who managed to capture Bannister with his jet, much to Lyla's delight.
It can implied that Bannister Evil Enterprises is presumably closed down following the arrest of Bannister and his cronies for their crimes.