s -> sh (e.g. "mister" -> "mishter") t/th -> ch or d (e.g. "take it easy" -> "chake id eajy", "the" -> "da") r -> w ("rub-rub" -> "wub-wub") l -> w ("lick-lick" -> "wick-wick")
Mix up the above and make up other replacements as appropriate (for instance, a lot of times "mama" is turned into "myamya" because there's no way to actually slur "mama" like "okaasan" can be slurred). Basically, just take what they're saying in English and turn it into the most over-the-top, infuriating, speech impediment laden baby-talk you can imagine.
"That's great" could be something like, "Dat'sh gweat!"
Yuu YuuWhere...?Haa... haa...I want it !Really ze?Hurry up noze, shitty slave!Where is it ? Where is it noze!?Munch Munch Easy !Uwa Uwa Uwa UwaGimme!It's because Reimyu is cute isn't it ?That's Reimyu's! Give it back ok?Sometimes even trash is good for something, huh?Now that they're gathering here, everyone please separate.Amajing! Amajing!Yuchi yuchinot yet ?Howd on, liddle shish noje!Here~ Come here~All of them is Maricha's nojeReimu will have one too !Big shish, huwwy up noje!Sweech Sweech ~~Where is the sweet sweet noze ?Hurry up and give us noje!I'll each a lot noje-!It's Reimyu's isn't it ?