Hannah Hart. That's all the explanation you're getting for this fic. Blame her and her adorableness.
Lisp
Kurt makes Blaine forget.
He makes Blaine forget about all kinds of things- homework that's due tomorrow, whatever he's been cooking when Kurt called, that thing he really had to do this afternoon, the fact he's scared of heights (well, that time he forgot about it for just a short moment), and, yeah, the fact that he has a "thlight lithp", too.
It's a lisp that doesn't really bother him when he sings- when there's a rhythm and the words keep flowing, his tongue doesn't feel the need to shove itself between his teeth.
It bothers him the most when he's talking to strangers or people that… aren't his friends.
He does have a lisp when he talks to Kurt, but he doesn't mind it that much. He doesn't mind because he knows Kurt thinks it's cute.
When they're alone, Kurt will always kiss him when he says words like "thoup" or "thnuggle" or "Thlytherin". When he greets Kurt with, "Hi thweetie!", it's not because he's slyly trying to get another kiss, but because Kurt just makes him forget.
He wasn't planning that make-out session on one boring Thursday afternoon; he just forgot it was a little difficult for him to say "do these jeans make my ass look as spectacular as yours?".
And he most definitely wasn't planning one of their almost-naked-make-out-sessions to become a very-naked-make-out-session-with-a-side-of-two-org asms-each. He just couldn't stop himself from crying, "Yeth, Kurt, oh my god, yeth, pleathe, more!" when Kurt finally slipped a hand underneath his boxers and started jerking him off, and "fathter, fathter, fathter!" when he was about to come. Needless to say, Kurt came even harder than he did, and suddenly, he didn't dislike having a lisp so much.
On their wedding day, though, Blaine did plan exactly how he'd say, loud and clear, "Yeth, I do."