It doesn’t matter if the stickers are on creatures. Any power and toughness stickers on noncreature permanents you control will also count.

If Ambassador Blorpityblorpboop has a power and toughness sticker on it, that sticker is included when calculating for the last ability.

Count only the powers and toughnesses of the stickers on permanents you control, not the actual powers and toughnesses of those permanents. For example, if a creature you control has a 4/4 sticker on it, but it also has three +1/+1 counters on it, it’s a 7/7 creature, but Ambassador Blorpityblorpboop’s base power and toughness would become 4/4.

Ambassador Blorpityblorpboop has received a minor update to clarify its function. Specifically, its ability causes its base power to match the total power of stickers you control, and its base toughness to match the total toughness of stickers you control. The updated wording appears above.

Although Ambassador Blorpityblorpboop’s last ability considers the power and toughness stickers of permanents you control, the card itself is not considered to be stickered unless there’s actually a sticker on it.

Ambassador Blorpityblorpboop counts all power and toughness stickers on all permanents you control, even if those power and toughness stickers don’t currently have any effect (possibly because you placed another power and toughness sticker on the same creature).

The base power and toughness change doesn’t end at end of turn; it lasts indefinitely, until Ambassador Blorpityblorpboop either leaves the battlefield or its base power and toughness changes again from another effect (for example, a power and toughness sticker being placed on it or its ability triggering again).