Red tongue and drooling

Bobke is a 4 year old DSH.  Today I noticed his lips were wet.  We couldn't see anything in his mouth so we figured he had just had a messy drink of water (not typical of him).  He hasn't really acted like himself but nothing really obvious.  Last night he slept with me which is unusual (too busy playing).  He hasn't wanted to go out in the garage (closed and no chemicals he can get into).  He sits by the door to go out there but changes his mind.  He tried to jump up onto the TV and missed when he has done that many times without fail.  I just noticed he's drooling.  Not just the wet lips but a long shoelace of slobber.  We looked into his mouth again and the tip of his tongue is red.  Has anyone seen anything like this?  I didn't notice anything different in our feeding ritual this morning but I'll make sure he's eating tonight.

He doesn't go outside.  He goes into our garage but it is always closed and we have no chemicals he can get into.  We leave the car maintenance to the professionals so no drip pans or puddles and our yard equipment is in a separate building.  I'm going to make an appointment tomorrow when the vet opens.

Update on Bobke:

He went to the vet Monday and it is still a mystery what happened to his tongue.  The vet said it looks like he burned it and the surface is sloughed off leaving the raw tissue exposed.  He gave us antibiotics (his breath stinks like it's infected) and pain killers along with some liquid diet to keep him going.  Once the pain killers took effect he was drooling less and ate some food.  Luckily, he's a chubby kitty so as long as we keep a little bit of food going into him and keep him hydrated he should be fine.  We're drawing a total blank on what he might have done.  All we've come up with is he could have licked a hot water pipe from our boiler??  Not sure why, after 3 winters of living with us, he would decide to do that but that's the only wild explanation we could come up with.