To 'pull an Alex' is to continuously put off something, even though you constantly assure everybody that whatever you are putting off, will be done.
The term is derived from the member Alex a.k.a. CurlyWurly on TeenHut forums, who made a thread regarding his yet-to-be shoutout video, that was never uploaded or posted, even though he repeatedly assured other members that it would be uploaded and posted "tomorrow".
1: Hurry up and get hard already!
2: Don't worry, I will. I'm not going to pull an Alex.
1: Did you hear about Bob?
2: Yeah, apparently he pulled an Alex.