So I thought I'd make a list of times Community was referenced by celebrities and other media, to show that its popularity is widespread and encompasses all sorts of awesome people. Despite its ratings.
So of course, I'll start with youtubers:
--Hank Green himself is a fan of community. He mentions Abed in this video.
and gets a Troy & Abed mug at the end of this video.
He also posts Community things on Tumblr sometimes, as in this link.
--charlieissocoolike gets a Troy & Abed mug here.
Also, he and Alex Day do Troy & Abed's hand shake near the end of this video.
Now for RL celebrities:
--Jasika Nicole (Astrid on Fringe): see Fringe link below.
And finally, other media references:
--Fringe!!! This is my favourite. (In the link, the beard is added. It's not really in the show, obviously.)
I know there are a lot more. I'll add them as I find them. Feel free to add more below!