Små grodorna - The little frogs is as close to a Swedish line dance as it gets and anyone who’s been to a Swedish Midsummer celebration has seen it performed. People gather around the Maypole and sing this song while jumping forward, mimicking little frogs and touching their ears or "tails" in time with the text. And everybody does it, from 3 year olds to parents, former and present prime ministers and consul generals.
How the song ended up in Sweden is unclear. What we do know is that the melody can be traced to a French military march from the days of the French Revolution, the so-called Onion Song "Löksången," or in French ”La Chanson de l’Oignon,” where in the chorus you sing ”Au pas, camarade, au pas camarade / au pas, au pas, au pas!" (In pace, companion!) It was France's sworn enemies who changed the text with classic British irony to ”Au pas, grenouilles!” (In pace, little frogs!) Somewhere along the way it acquired a Swedish text about frogs and became an important part of our Swedish cultural heritage ... and you can trust us when we say with conviction that no Swedish Midsummer can be celebrated without it!

Other popular songs to sing around the Maypole are:
Och flickan hon går i dansen
Prästens lilla kråka
Höga berg och djupa dalar
Jag gick mig ut en afton
Sju vackra flickor i en ring
Så går vi runt om ett enrissnår
Uppå källarbacken
Vi äro musikanter
Karusellen
Morsgrisar är vi allihopa
Raketen

Just in case you're visiting your first Swedish party this year, here is the grodsången lyrics in Swedish:

Små grodorna, små grodorna är lustiga att se.
Små grodorna, små grodorna är lustiga att se.
Ej öron, ej öron, ej svansar hava de.
Ej öron, ej öron, ej svansar hava de.
Kou ack ack ack, kou ack ack ack,
kou ack ack ack ack kaa.
Kou ack ack ack, kou ack ack ack,
kou ack ack ack ack kaa.

English translation:
The little frogs, the little frogs are funny to observe.
The little frogs, the little frogs are funny to observe.
No ears, no ears, no tails do they possess.
No ears, no ears, no tails do they possess.
Kou ack ack ack, kou ack ack ack,
kou ack ack ack ack kaa.
Kou ack ack ack, kou ack ack ack,
kou ack ack ack ack kaa.
(There's a second verse about the little pigs but let's not get complicated here. Just do what everyone else does and you'll be fine.)