This expression of Snoopy's cracks me up:

Here's a rather poor scan of the strip that image is taken from, for context:That is apparently the face Snoopy makes when he's feeling sick from having had too much to eat and drink. That may explain why the face looked so strange to me, as it's certainly not one that shows up in many Peanuts strips, unlike the expressions he makes in the third and fourth panels.

The strip was scanned from the May 25 issue of the Ashtabula County Star Beacon.