They were originally enemies in Season 3, but then allied after Lotor killed Emperor Zarkon. They then worked together as allies for a while, during which Lotor developed feelings for Allura and Lance got jealous of Lotor and started feeling he could never compare to the prince. Then Lotor was revealed to be evil courtesy of Keith, Krolia, and Romelle, and they went back to being straight-up enemies again.
Before Lotor was officially introduced on the show, fans would theorize as to how he would interact with the Paladins. Some fans thought that Lance would be in some way jealous of Lotor's hair, and his flirting with Allura. There were also a lot of fan art of evil Lance alongside Lotor. Royalty AU's are also popular in the pairing.
Some will depict Lotor flirting with Lance and ignoring Allura, in both fan art and fan fiction. Snarky back and forth are also popular as well. Typically when Lotor flirts with Lance, he will snarkly reject him. Normally Lance is being shown to be put off by Lotor's advances. The darker side of these portrayals, show Lotor pursuing Lance past the point of comfort and hurting the other paladins in the process.
On AO3, Lancelot is the 14th most written ship within the fandom; Lotor's most written and Lance's fifth.
|SHIPS||het||Allurance • Allurivan • Hallura • Hidge • Hunay • Hunelle • Jamonica • Kacxa • Kallura • Kidge • Komelle • Krolidad • Krolivan • Leiffin • Lotacxa • Lotura • Mallura • Nymatt • Plance • Romatt • Romance • Shallura • Shidge • Zaggar|
|slash||Adashi • Corance • Hance • Heith • Jaith • Katt • Keitor • Klance • Koliveith • Lancelot • Latte • Shance • Sharkon • Shatt • Sheith • Shendak • Shlav • Shoran • Shotor • Shunk • Svance • Svav • Sveith • Uliro|
|femslash||Acxlura • Kromelle • Pallura • Romura • Shayllura • Veracxa • Zezor|
|poly||Jeiro • Klunk • Pallurance • Sheitor • Shkatt • Shklance|
|CHARACTERS||m/f||Allura • Hunk • Keith • Lance • Lotor • Matt • Pidge • Shiro|