Question: What did residents claim to encounter one evening in 1955 on US 41 at Kelly, Kentucky, leading to an annual festival of Little Green Men?

Context articles: Little Green Men (The X-Files)
Kelly, Kentucky
U.S. Route 141
Kelly–Hopkinsville encounter
Interstate 41
Kentucky Route 425
U.S. Route 41 Business (Marquette, Michigan)
U.S. Route 41
Enanitos Verdes
U.S. Route 41 in Florida

"Little Green Men" is the first episode of the second season of the science fiction television series "The X-Files".
 It premiered on the Fox network on September 16, 1994 in the United States.
 It was first broadcast in the United Kingdom on BBC Two on August 28, 1995.
 The episode was written by Glen Morgan and James Wong, and directed by David Nutter.
 The episode helped explore the series' overarching mythology.
 "Little Green Men" earned a Nielsen household rating of 10.3, being watched by 9.8 million households in its initial broadcast.
 The episode received largely positive reviews from critics.
Kelly is an unincorporated community in Christian County, Kentucky, in the United States.
 Kelly is located at (38.218373, -85.353058), on U.S. Route 41.
 It is best known for being the location of the 1955 Kelly-Hopkinsville alien encounter, in which residents reported seeing unidentifiable creatures and lights at a rural farmhouse.
 In honor of this event, the community hosts the Kelly "Little Green Men" Days festival each year, where visitors can buy "intergalactic souvenirs".
US Highway 141 (US 141) is a north–south United States Numbered Highway in the states of Wisconsin and Michigan.
 The highway runs north-northwesterly from an interchange with Interstate 43 (I-43) in Bellevue, Wisconsin, near Green Bay, to a junction with US 41/M-28 near Covington, Michigan.
 In between, it follows city streets in Green Bay and has a concurrent section with US 41 in Wisconsin.
 North of Green Bay, US 141 is either a freeway or an expressway into rural northern Wisconsin before downgrading to an undivided highway.
 In Michigan, US 141 is an undivided highway that runs through rural woodlands.
 The highway has two segments in each state; after running through Wisconsin for about 103 mi , it crosses into Michigan for approximately another 8 mi .
 After that, it crosses back into Wisconsin for about 14+1/2 mi before crossing the state line one last time.
 The northernmost Michigan section is about 43+1/2 mi , making the overall length about 169 mi .
The Kelly–Hopkinsville encounter (a.k.a. Hopkinsville Goblins Case, Kelly Green Men Case) was a claimed close encounter with extraterrestrial beings in 1955 near Kelly and Hopkinsville in Christian County, Kentucky, United States.
 UFOlogists regard it as one of the most significant and well-documented cases in the history of UFO incidents, while skeptics say the reports were due to "the effects of excitement" and misidentification of natural phenomena such as meteors and owls. Psychologists have used the alleged incident as an academic example of pseudoscience to help students distinguish truth from fiction.
Interstate 41 (I-41) is a 176.33 mi Interstate Highway connecting the interchange of I-94 and U.S. Route 41 (US 41), located 0.9 mi south of the Wisconsin–Illinois border at the end of the Tri-State Tollway in metropolitan Chicago, to an interchange with I-43 in metropolitan Green Bay, Wisconsin.
 The designation travels concurrently with US 41, I-894, US 45, I-43, and sections of I-94 in Wisconsin and Illinois.
 The route was officially added to the Interstate Highway System on April 7, 2015, and connects Milwaukee and the Fox Cities with Green Bay.
Kentucky Route 425 (or Henderson Bypass) is the Southern Beltline around Henderson, Kentucky.
 It is a two-lane road that runs from US 60/KY 136 east to Pennyrile Parkway (future I-69) and intersects with US 41A, KY 1299, and US 41.
 It is a rural highway that is all at grade intersections.
 At the US 41A junction, rumble strips are used to alert traffic to the intersections.
Business US Highway 41 (Bus.
 US 41) was a state trunkline highway that served as a business loop off US 41 and M-28 in Marquette, Michigan, along Washington and Front streets.
 The streets serve the downtown area of Marquette and are bordered by several commercial properties and businesses.
 Those two streets originate with the early founding of the city in the middle of the 19th century.
 Jurisdiction over them was transferred to the city as part of a highway swap that resulted in the decommissioning of the trunkline in 2005.
 It was also previously co-designated Bus.
 M-28, mirroring the Bus.
 US 41/Bus.
 M-28 designation previously used along Bus.
 M-28 in Ishpeming and Negaunee.
 Washington and Front streets had been a part of the state highway system since the 1910s, and a part of the United States Numbered Highway System since 1926.
 The business loop designation dates back to the 1960s and was removed in 2005.
U.S. Route 41, also U.S. Highway 41 (US 41), is a north–south United States Highway that runs from Miami, Florida to the Upper Peninsula of Michigan.
 Until 1949, the part in southern Florida, from Naples to Miami, was US 94, which presently has the hidden designation of State Road 90 (SR 90) in addition to its signed number.
Enanitos Verdes (Literally "Little green dwarfs", roughly equivalent to the English phrase "Little green men") is a rock trio from Argentina, formed in 1979 in the city of Mendoza.
U.S. Route 41 (US 41) in the U.S. state of Florida is a north–south United States Highway.
 It runs 479 mi from Miami in South Florida northwest to the Georgia border north of the Lake City area.
 Within the state, US 41 is paralleled by Interstate 75 (I-75) all the way from Miami to Georgia (on the northern border), and I-75 has largely supplanted US 41 as a major highway.