Esper got hunted down and killed several times by (iirc Talespin, but it may have happened in other matches as well). After casters pointed that out and noted (perhaps incorrectly) that LG had several skirmishes in a row without Esper's rez, twitch chat caught on, and started spamming "Remove Esper" (or something similar) every time Esper died.
Hence the joke.