Origins: the infamous Crystalwank of FandomWank.
A popular internet catchphrase used to
sarcastically denote obvious falseness or lying.
The full original quote, "MY HED IS PASTED ON YAY", comes from the above FandomWank thread wherein a LiveJournal user named Crystal attempted to convince her readers that she was real-life friends with a cast member of
the Lord of the Rings films by making very obvious photo-manipulations of the actors in various poses in her room. These photos were quite clearly pictures of the actor's heads transposed onto different bodies.
The thread became monstrous in a very short time, eventually receiving over 13,000 comments. In the course of the thread, a commenter remarked that one of Crystal's photos wore a look of 'OmG my head iz PASTEDE ON YAY!!1111!!' The remark quickly spread across the Internet, where it was adopted and adapted. This FandomWank thread, especially the "pastede on" comment, is considered something of a Holy Grail of
internet slang.
See also pastede, my hed is pastede on, yay.
Since the initial wank, anything may be
regarded as "pastede on yay". A bad writer can be accused of having his/her
spelling (or grammar, or ideas) "pastede on yay!" A fruity drink that does not taste
particularly fruity might be said to have its "fruitiness pastede on yay!"